To provide a head supporting device for an operating chair which can be reliably fixed by simple operations without displacement of its pillow and which can be used even when there is no driving force for its hydraulic cylinder.

A proximal end of a first arm is rotatably coupled to a bracket of a backrest of the chair on a shaft for arm as a first joint. A proximal end of a second arm is coupled to a bracket of the pillow on a shaft as a third joint. A leading end of the first arm and a leading end of the second arm are rotatably coupled to each other on a shaft for arm as a second joint. In this way, the device has at least three joints. Each of the joints is provided with an independent electromagnetic brake for attachment and detachment of the joint. Gears are interposed between the shaft for arm and the shaft for brake. A high brake torque is obtained by providing a gear on the shaft for brake with sufficiently smaller number of teeth than those of the gear on the shaft for arm and engaging them in each other.