A surgical system (I) is provided with: a first medical instrument (2) that is disposed inside a body cavity and that has an observation unit (22) and a marking unit (23) that is capable of being positioned with respect to the body cavity a second medical instrument (4) that is disposed outside the body cavity and that has a treatment section (42) and a driving unit (44) for driving the treatment section (42) a distance measuring unit (8) that measures the distance between the marking unit (23) and the treatment section (42) and a control unit (61) that controls the driving unit (44) on the basis of the distance measured by the distance measuring unit (8).
