(a) a base portion at which a predetermined first axis is set and in which an internal space is formed so that a cable can be inserted into the internal space;

(b) a first reduction device having a hollow structure and mounted on the base portion, the first reduction device including a first input axis part and a first output axis part so that a rotation applied to the first input axis part is reduced and transmitted to the first output axis part, the first output axis part being configured to be rotatable about the first axis, and a first through hole being formed in the first reduction device so as to extend coaxially with the first axis and communicate with the internal space of the base portion;

(c) a first driving device mounted on the base portion and adapted to apply a rotation to the first input axis part of the first reduction device;

(d) a first movable portion fixed to the first output axis part of the first reduction device, a second axis being set at the first movable portion such that the second axis extends vertically to the first axis in a position spaced away from the base portion in the first axial direction, the first movable portion forming a first movable portion space to extend back along the first axial direction, pass through the second axis, and communicate with the first through hole;

(e) a second reduction device mounted on the first movable portion, the second reduction device including a second input axis part and a second output axis part so that a rotation applied to the second input axis part is reduced and transmitted to the second output axis part, the second output axis part being located in a position spaced away from the first axis in the second axial direction and configured to be rotatable about the second axis;

(f) a second driving device mounted on the first movable portion and adapted to apply a rotation to the second input axis part of the second reduction device;

(g) a second movable portion fixed to the second output axis part of the second reduction device, a third axis being set so as to pass through a position nearer to the first axis than the second output axis part of the second reduction device in the second axial direction and extend vertically to the second axis, the second movable portion forming a second movable portion space to communicate with the first movable portion space passing through the second axis and extend along the third axial direction;

(h) a third reduction device having a hollow structure and mounted on the second movable portion, the third reduction device including a third input axis part and a third output axis part so that a rotation applied to the third input axis part is reduced and transmitted to the third output axis part, the third output axis part being configured to be rotatable about the third axis, a third through hole being formed in the third reduction device so as to extend coaxially with the third axis and communicate with the second movable portion space;

(i) a third movable portion fixed to the third output axis part of the third reduction device, the third movable portion being configured such that an end effecter can be attached thereto, the third movable portion forming a third movable portion space to extend coaxially with the third axis and communicate with an external space from the third through hole; and

(j) a third driving device mounted on the second movable portion and adapted to apply a rotation to the third input axis part of the third reduction device, the third driving device being located opposite to the third reduction device relative to the second movable portion with respect to the third axial direction and disposed to be spaced away from the third axis in the direction vertical to the third axis,

wherein the third driving device is disposed to be spaced away from the third axis in the second axial direction, and

wherein the second reduction device and the third driving device are arranged side by side across the third axis along the second axial direction.