To switch a desk to a non-used position wherein the desk is folded along the back side of the desk by providing a restraining means which restrains the movement of a link by being detachably engaged with the link at a using position.

An auxiliary table 11 is rotatably connected to a desk 12 by a first link 13 and a second link 14 respectively at the front end and the rear end, and is switched to a non-used position wherein the auxiliary table 11 is joined to the back side of the desk and folded, and a using position wherein the auxiliary table 11 stands up on the desk. At the using position, the first link 13 is placed under a forward fallen state, and is engaged with a stopper pin 15 which is projected from the desk 12, and is prevented from falling further. Even if a load is applied on the auxiliary table 11 under this state, since the first link 13 is stopped by the stopper pin 15, the auxiliary table 11 is kept at the using position. When the auxiliary table 11 is switched to the non-used position, a hook 17 is removed from a pin 16, and then, the auxiliary table is pushed down, and the auxiliary table under the non-used position wherein being folded on the back side of the desk, can be placed under the main desk.