forming a wiring board having a wiring layer on each face of an insulating layer;

forming a conductor press-fit hole comprising forming a through hole in said wiring board in a thickness direction of the wiring board to connect said wiring layer on each face of the insulating to each other;

press-fitting a generally spherical conductor having a larger diameter than that of said conductor press-fit hole into said conductor press-fit hole to expand and deform the wiring layer around said conductor press-fit hole on the press-fit side, to the outside and to joint said wiring layer expanded to the outside, and the conductor to each other, the generally spherical conductor and conductor press-fit hole forming cone-shaped portions contacting each other; and

feeding particle solder members in a predetermined quantity into the conductor press-fit hole on the side opposite to said press-fit side, and melting and solidifying said solder members to joint said conductor filled and press-fitted in said conductor press-fit hole and to joint the wiring layer around said conductor press-fit hole on the opposite side.