A trocar comprising: a housing； an insertion tube that is integral with the housing and is inserted into a subject； a power transmission coil that is disposed inside of the housing and generates AC magnetic field to be applied to an insertion hole into which a treatment tool is to be inserted； a radiator that transmits heat generated from the power transmission coil； and a heat insulator disposed on a side of the subject between the radiator and the subject, the heat insulator having lower thermal conductivity than the radiator.
