To provide a fitting structure facilitating regulation of position and simplifying execution of construction without using an adhesive, on the occasion of fitting an interior material such as a plaster board to a building frame such as a concrete panel, a concrete wall or an ALC panel.

A substrate fitting material A having a plate body 1 and a prepared screw hole part 2 wherein a prepared screw hole provided with a plurality of projections is formed is disposed at prescribed intervals in the vertical and lateral directions of a building frame 11. A screw 5 is screwed in the prepared screw hole 4, the head part 5b thereof is made to reach a cup- shaped part 2a and the fore end thereof is made to project. The screw 5 is screwed in and fixed to the building frame 11 in this state and further the substrate fitting material A is rotated to make the plate body 1 accord with a reference plane 12. An interior material 13 is brought into contact with the plate body 1 made to accord with the reference plane 12 and is fixed by fixation fittings 14. A wooden substrate is fitted on the plate body 1 of the substrate fitting material A and the interior material 13 is fixed on this wooden substrate.