a rotor core being rotatable around a rotational axis, the rotor core including a plurality of steel plates stacked in a stacking direction parallel to the rotational axis and having a plurality of magnet insertion holes at every first circumferential space, each of the plurality of steel plates comprising:

a plurality of magnet insertion piece holes provided at every said first circumferential space, the plurality of magnet insertion piece holes constituting the plurality of magnet insertion holes when the plurality of steel plates are stacked in the stacking direction while the plurality of steel plates are rotated by the first circumferential space and a predetermined number of the plurality of steel plates are stacked in the stacking direction;

a plurality of through piece holes penetrating each of the plurality of steel plates at every second circumferential space in the stacking direction on a radially inner side of the plurality of magnet insertion piece holes, the first circumferential space and the second circumferential space being different from each other;

a radially inner side annular ring provided on a radially inner side of the plurality of through piece holes;

a radially outer side annular ring provided on a radially outer side of the plurality of through piece holes; and

a plurality of ribs provided between the plurality of through piece holes and connecting the radially inner side annular ring and the radially outer side annular ring,

wherein a first one of the magnet insertion piece holes of a first one of the steel plates entirely overlaps a second one of the magnet insertion piece holes of a second one of the steel plates when viewed in the stacking direction, and

wherein a first one of the through piece holes of the first one of the steel plates partially overlaps a second one of the through piece holes of the second one of the steel plates when viewed in the stacking direction.