A trocar sensor unit including a base that is configured to be attached to and detached from a trocar and that has a through-hole through which an insertion section to be inserted into the trocar is inserted； a moving member that has a pressing surface forming at least a portion of an inner surface of the through-hole of the base and that is configured to be moved in a radial direction of the through-hole； and a sensor that is disposed in at least one of the moving member and a portion of the inner surface of the through-hole opposite the pressing surface and that detects the amount of movement of a surface of the insertion section in the through-hole.
