To enable spaces between a main top plate and auxiliary top plates to be freely set according to a service purpose or the like.

The main top plate 21 is supported with a support frame 1 where upper ends of right and left leg bodies 2 are connected by transverse rods 3 and 4. At least one side end of connection rod 3 extends outward from the leg body 2 and the main top plate 21. A support member 36 provided on the extension part 3a and transversely changeable in a position supports the back end of the assistant top plate 31 having a support leg 33 provided on the bottom of the front end and standing on a floor.