To provide a mounting structure of a floor joist in a floor panel capable of easily corresponding to the floor joist even if the floor joist interferes with something else.

A slit 6 for passing through a screw metal fitting for penetrating in the vertical direction extended to a direction at right angles to the direction of the floor joist is formed in a face plate 2, the floor joist 3, etc., is fixed on the lower surface side of the face plate 2 with screw metal fittings 4 and 5 penetrated through the slit 6, the screw metal fittings 4 and 5 can be moved in the slit 6 in a state to loosen them, and a fixing position of the floor joist 3 can be changed in the direction at right angles to the direction of the floor joist.