PURPOSE: To surely stick the fellow floor panels made of aluminum extruded material fast to each other by setting a plurality of pendent walls on the side of one floor panel in the recesses on the other floor panel, and also, engaging both pendent engaging projections with the engaging projections on the other floor panel side.

CONSTITUTION: In condition that the horizontal wall 22 of the left connection edge 20a of the second floor panel 20 is fixed to the floor supporting member 7 under the load-carrying platform 3 by a bolt 8, the first and second pendent walls 11 and 12 for coupling on the side of the first floor panel 10 are set in the recesses 24 on the side of the second floor panel 20 from above. Thereupon, the right engaging projection 13 at the tip of the first pendent wall 11 for coupling falls along the vertical wall 221 for coupling on the side of the second floor panel 20, and engages with the left engaging projection 25 at the section positioned a little to the bottom of the vertical wall 21 for coupling from below. On the other hand, likewise the second pendent wall 12 for coupling falls along the rise wall 23, and a left engaging projection 15 engages with a right engaging projection 27. The tip of the second pendent wall 12 for coupling is inserted into the socket 30 on the side of the second floor panel 20, and both right and left floor panels 10 and 20 are coupled together.