A surgery supporting apparatus capable of performing a manipulation using a surgical instrument to be inserted into a body cavity, comprises a measurement device configured to measure an insertion depth and an insertion angle, with respect to the body cavity, of a shaft of the surgical instrument inserted into the body cavity, as input of the manipulation, wherein the measurement device measures the insertion depth by measuring a sound wave propagating in a space between a transmitter attached to one of the surgical instrument and a position within a predetermined range from a position of insertion to the body cavity, and a receiver attached to the other.