A method for detecting an air leak in an endoscope device, comprising: providing a leak tester for inspecting presence or absence of an air leak in an endoscope device, comprising: an air pump for supplying air into the endoscope device; a pressure sensor that detects a pressure inside the endoscope device; and a control unit that controls operation of the air pump and the pressure sensor and judges the presence or absence of an air leak from the endoscope device, executing, by the control unit: operation of the air pump to supply air into the endoscope device to increase the pressure inside the endoscope device to a predetermined value; a first process of judging whether an internal pressure of the endoscope device has dropped from said predetermined level, by a first pressure value within a first time span of within 10 seconds after start of a wet test, wherein at the start of the wet test an operator immerses the endoscope in water of a water tank; a second process of judging whether the internal pressure has further dropped, by a second pressure value different from the first pressure value within a second time span different from the first time span in a case where the internal pressure has dropped, by the first pressure value in the first process; a process of judging pass or fail in the wet test on the basis of a result of the second process; characterized in that the method further comprises a third process of judging whether the internal pressure has further dropped, by a third pressure value different from the first pressure value within a third time span different from the first time span, in a case where the internal pressure has not dropped by the first pressure value in the first process, wherein the third process is conducted after one minute from the start of the wet test; and a process of judging pass or fail in the wet test on the basis of a result of the third process. providing a leak tester for inspecting presence or absence of an air leak in an endoscope device, comprising: an air pump for supplying air into the endoscope device; a pressure sensor that detects a pressure inside the endoscope device; and a control unit that controls operation of the air pump and the pressure sensor and judges the presence or absence of an air leak from the endoscope device, an air pump for supplying air into the endoscope device; a pressure sensor that detects a pressure inside the endoscope device; and a control unit that controls operation of the air pump and the pressure sensor and judges the presence or absence of an air leak from the endoscope device, executing, by the control unit: operation of the air pump to supply air into the endoscope device to increase the pressure inside the endoscope device to a predetermined value; a first process of judging whether an internal pressure of the endoscope device has dropped from said predetermined level, by a first pressure value within a first time span of within 10 seconds after start of a wet test, wherein at the start of the wet test an operator immerses the endoscope in water of a water tank; a second process of judging whether the internal pressure has further dropped, by a second pressure value different from the first pressure value within a second time span different from the first time span in a case where the internal pressure has dropped, by the first pressure value in the first process; a process of judging pass or fail in the wet test on the basis of a result of the second process; characterized in that the method further comprises a third process of judging whether the internal pressure has further dropped, by a third pressure value different from the first pressure value within a third time span different from the first time span, in a case where the internal pressure has not dropped by the first pressure value in the first process, wherein the third process is conducted after one minute from the start of the wet test; and a process of judging pass or fail in the wet test on the basis of a result of the third process. operation of the air pump to supply air into the endoscope device to increase the pressure inside the endoscope device to a predetermined value; a first process of judging whether an internal pressure of the endoscope device has dropped from said predetermined level, by a first pressure value within a first time span of within 10 seconds after start of a wet test, wherein at the start of the wet test an operator immerses the endoscope in water of a water tank; a second process of judging whether the internal pressure has further dropped, by a second pressure value different from the first pressure value within a second time span different from the first time span in a case where the internal pressure has dropped, by the first pressure value in the first process; a process of judging pass or fail in the wet test on the basis of a result of the second process; characterized in that the method further comprises a third process of judging whether the internal pressure has further dropped, by a third pressure value different from the first pressure value within a third time span different from the first time span, in a case where the internal pressure has not dropped by the first pressure value in the first process, wherein the third process is conducted after one minute from the start of the wet test; and a process of judging pass or fail in the wet test on the basis of a result of the third process.