A surgery supporting apparatus is capable of controlling a posture of a first surgical instrument that is inserted into a body cavity and mechanically drivable, by using a second surgical instrument to be inserted into the body cavity. The apparatus comprises a robot arm configured to control the posture of the first surgical instrument attached to the robot arm. Instructions stored in a memory cause the apparatus to function as a control unit configured to control the motion of the robot arm such that the posture of the first surgical instrument is controlled in accordance with the posture of the second surgical instrument, in a case of a first mode, and controls the motion of the robot arm in accordance with a manipulation including contact to the robot arm, in a case of a second mode.
