To improve noise insulation performance by placing an end portion of lightweight foamed concrete on a ribbed receiving fittings, fixing the ribbed portion of the receiving fittings to a beam, and filling mortar between the whole surface of the connecting portion of the panel and the whole surface of the top surface.

A rib 3 is provided in a direction perpendicular to the attaching surface 5 contacted and fixed to a web 7 of an H-shaped beam 6, and a ribbed receiving fittings 2 is formed by providing a long-sized L-shaped fittings 4 in parallel to and in one united body with the H-shaped beam 6, on which the end portion of the lightweight foamed concrete panel 1 can be placed on the rib 3. And at both the sides of the web 7 of H-shaped beam 6, an attaching surface of 5 of the ribbed receiving fittings 2 is contacted and fixed. And the end portion of the panel 1 is placed on the side piece of an L-shaped fittings 4 of the ribbed receiving fittings 2, and mortar 9 is filled in the gap between the header surface of the panel 1 and the L-shaped fittings 4. In addition, a layer of mortar 10 is provided on the whole top surface of the panel 1 and mortal 9 portion. In this way, the noise insulation performance against heavy floor impact sounds can be improved without increasing the dimension between the floor and ceiling compared to the conventional one.