PURPOSE: To keep a moving sense between a chair sitting position and a lying position felt by a patient satisfactorily by lifting the front side of a sitting seat supporter to locate the knee part of the patient higher than the waist part and inclining a bearing surface in that direction.

CONSTITUTION: The front part of the sitting seat supporter 1 performs such motion to be lifted upward centering about a setting seat supporting shaft 1a as a driving source 5 is operated and a slidable arm 5a is extended. At this time, since the prescribed position of the intermediate part of a first lower rocking arm 3 is attached pivotally on the lover side of the front terminal of the setting seat supporter 1, the arm 3 starts to move simultaneously. Consequently, a roller 4 bonded on the lower terminal part of the first lower rocking arm 3 presses the back of an upper rocking arm 2, and the upper rocking arm 2 follows the motion of the lower rocking arm 3. In this way, the upper rocking arm 2 is also operated so as to form a prescribed angle for a horizontal line by inclining the bearing surface in a direction to lift the front side of the sitting seat supporter 1.