To fix a drawer at an optional position by locking and unlocking by simple operation at the drawer for housing a keyboard.

The drawer 30 is provided with a locking device 50 capable of locking and unlocking at an optional position with respect to a drawer housing frame 40. This device 50 is provided with an operation lever 52 along the bottom plate 38 of the drawer 30, right/left L-shaped links 54 rotated with a supporting pin 55 in a center by pulling the lever 52 to this side and lock pieces 56 drawn in from receiving holes 46 plurally formed in the longitudinal direction of the side frame 42 of the frame 40 by the rotation of the links 54, returned by releasing the lever 52 from one's hand and fitted into an optional receiving hole 46. The pieces 56 are returned by the elastic force of a compressed spring 62.