PURPOSE: To prevent occurrence of stress corrosion cracking, pitting corrosion, etc., in a heat exchanger tube by making the resident time of the water in the pipe shorter at the time of inspecting the tube while the tube is used by inserting a draining device into the tube from one end when a probe is sent into the tube from the other end.

CONSTITUTION: At the time of the inspection of a U-shaped heat exchanger tube 20 of a heat exchanger while the tube is used, a nondestructive test is carried out with a probe 4 while the tube 20 is filled up with water and the tube 20 is drained by means of a draining device 8 after the test. The probe 4 is sent into the tube 20 toward the tube plate 7 at one end of the tube 20 from the tube plate 3 at the other end by means of a probe driving mechanism 1. When the probe 4 is sent into the tube 20 toward the tube plate 7 side, the draining device 8 is inserted into the tube 20 from the tube plate 7 side by means of a draining device driving mechanism 5 and the device is allowed to suck the water in the tube 20 in the vicinity of the lowest section of the tube 20. Therefore, the tube 20 is drained by the device 8 immediately after the nondestructive test. Thus the resident time of the water in the tube 20 can be shortened sharply.