To facilitate the processing of a vertical frame notch part for fitting a floor support material, and to improve the reliability of fitting strength of the floor support member.

In the joint structure between a wall panel and a floor panel, the end part of the floor panel 12 is joined to the inside face of the wall panel 11 having a plurality of vertical frames 17. In this case, notch parts 25 are formed at about the same height in the vertical frame 17 of the wall panel 11, and a floor support member 26 and a through member 27 are fitted and fixed to the notch part 25 with the floor support material set in a protruded state, and the end part of the floor panel 12 is mounted on the floor support member 26 and fixed to the wall panel 11 with a nail 31.