PROBLEM TO BE SOLVED: To perform leak test accurately on an existing endoscope by adding a temperature sensor to the endoscope without making the endoscope larger and more complicated.SOLUTION: A control unit 19 opens a conduit valve 14, closes an exhaust conduit valve 15, sucks air from an endoscope 2 by an air pump 11, detects the conduit temperature Tp by a conduit temperature sensor 17, and detects the outside air temperature TA by an atmospheric temperature sensor 18. The control unit 19 calculates the temperature deviation &Dgr；T of the conduit temperature Tp to the outside air temperature TA. When the absolute value &Dgr；T of the temperature deviation is equal to or greater than the threshold value Tmax, the control unit 19 waits until &Dgr；T becomes smaller than the threshold value Tmax, repeating introduction and suction of air to and from within the endoscope 2. On the other hand, when &Dgr；T is smaller than the threshold value Tmax, the control unit 19 sets the threshold value Dp for determination of leakage according to the temperature deviation &Dgr；T, and executes leak test using the threshold value Dp for determination of leakage.SELECTED DRAWING: Figure 1
