Abstract: A surgical trocar includes a connection unit, which: connects a first trocar body and a second trocar body such that the second trocar body can vertically move relative to the first trocar body when a trocar unit is inserted into and drawn out of a trocar body unit having the first trocar body and the second trocar body, such that when an external force is not applied, a state of being unfolded in the radial direction of the first trocar body is maintained; and has an extension member extending in the longitudinal direction of the first trocar body when the trocar unit is inserted into the trocar body unit such that the second trocar body moves relative to the first trocar body.