A trocar 10 includes: a housing 14； an insertion tube 14H that is integral with the housing 14 and is inserted into a subject 9； a power transmission coil 11 that is disposed inside of the housing 14 and generates AC magnetic field to be applied to an insertion hole 10H into which a treatment tool 30 is to be inserted； a heat dissipation member 12 that transmits heat generated from the power transmission coil 11； and a heat insulation member 13 disposed on a side of the subject with reference to the heat dissipation member 12 and having lower thermal conductivity than the heat dissipation member 12.
