An operating mechanism of medical device includes a first shaft, a driving source which generates an auxiliary driving force, a second shaft which is operated by the auxiliary driving force, a connecting part which connects the first motion transmission part with the second motion transmission part, transmits the auxiliary driving force from the second motion transmission part to the first motion transmission part, wherein at least a part of the connecting part is capable of an elastic deformation; a detecting unit which detects at least one of a first operation amount of the first motion transmission part and a second operation amount of the second motion transmission part; a control unit that which controls the driving source based on the first operation amount and the second operation amount detected by the detecting unit; and a regulating unit which regulates so that an amount of the elastic deformation of the connecting part is equal to or more than a predetermined amount.