To enable a top plate used for assembling furniture and folding furniture to be freely designed in size and shape and to be disassembled in small pieces at need.

In a top plate 5 for a table, a shelf, etc., constituted by adhering side parts of plural plates, a hollow part 3 is formed on the side part of a plate member 2. On the other hand, a protruding joint part 4 protruding from the other side face part of the plate member 2 to enable the joint member 4 to be fitted in the hollow part 3, and a fixing means to enable the fitting condition to be fixed is placed and formed on the top plate, or an attaching member with the hollow part 3 formed on the side face part and a joint member 4 insertable into the hollow part 2 are used for constituting the top plate.