When an air supply conduit is connected to an empty space portion inside an endoscope and air is fed to the empty space portion to perform a leak determination based on a change in the internal pressure of the endoscope which is caused by the air, a surface temperature of the endoscope that is measured by a temperature measurement portion is maintained at a temperature at the time that the leak determination starts, through energy supply control that irradiates far infrared rays onto a surface of the endoscope from a far-infrared ray irradiation portion.