To provide a folding apparatus of a top plate in which folding operation is extremely simple.

The folding apparatus of a top plate is provided with a turn connection means 2 wherein: turn supporting base plates 10 comprising fixing pieces 11 to be fitted to top plates 1A and 1B and vertical pieces 12 projecting from the fixing pieces 11 are fixed in a symmetrical layout corresponding to a pair of the top plates 1A and 1B; one end sides 13a of a pair of rotation arms 13 nearly in a U-shape which cross with each other under the abutting position of a pair of the top plates 1A and 1B and supported turnably by a shaft 14 are engaged respectively slidably with slide long grooves 15 formed at both of the vertical pieces 12; and the respective other end sides 13b of a pair of the arms 13 are turnably fitted to the vertical pieces 14 on the other side mutually at the lower part of the neighborhood of the abutting position of a pair of the top plates 1A and 1B respectively. Thus, a pair of the top plates 1A and 1B can be folded in the contacting direction of the surface side of each other with the shaft 14 of the rotary connection means 2 as a spindle.