PURPOSE: To enable a shelf to be moved up and down while mounting on a frame and to adjust its position in such a way as it may be slid freely by a method wherein a stopper claw is provided at a shaft having a gear fixed to a deep side of the frame holding the shelf and a guide pin, a rack engaging with the gear and a rack-like stopper groove with the stopper claw are formed.

CONSTITUTION: When a shelf 9 is moved up and down, at first an operator's side of a frame 10 is lifted up to cause a stopper claw 14 fixed to the frame 10 to be released from a rack-like stopper groove 17 and then a gear 12 fixed to a shaft is rotated while being engaging with it. Then, the frame 10 is moved up and down directly along a rail 15. At this time, if the shelf 9 reaches its target position, an operator's side of the frame 10 is returned to its original horizontal position, resulting in that the stopper claw 14 and the rack-like stopper groove 16 are engaged and they are kept at their positions with a force for stopping rotation of a shaft 11 and a frictional rotating force of the gear 12. A sliding groove 15a stores a part of a guide pin 13 formed in the rail 15 and keeps its sliding movement.