PURPOSE: To prevent stiff shoulders and to reduce the fatigue of muscles by resting elbows when a worker works at the desk by providing an elbow rest part for resting elbows of the worker, who comes to the desk in a sitting posture, and a recessed part for receiving the worker at the sitting posture.

CONSTITUTION: This elbow rest plate 10 for preventing stiff shoulders is provided with an elbow rest part 11 on its upper face and slidable engaged to a desk 12. Namely, guide rails 26 with L-shaped cross-sections are arranged on both sides and center of a main body plate 22, and the elbow rest plate 10 is held between guide rails 26 and 16 so as to be freely slid. A front stopper 28 and a rear stopper 30 for preventing the elbow rest plate 10 from pulling off are provided at both the terminals of the guide rail 26. Two pieces of elbow rest plates 10 are arranged in axial symmetry to the central guide rail 26. Besides, the elbow rest plate 10 is provided with a recessed part 32 in the shape of a 1/4 circle, and the worker can be received at the semicircular recessed part formed by the cooperation of two elbow rest plates 10.