PURPOSE: To accurately and promptly accomplish the moisture resistance tests with the use of a simple mechanism by using a cover plate to which a water nozzle is attached.

CONSTITUTION: There are attached to a frame 1 a water bath 2, to which a suction pump 17 is connected, a receiving dish 13, a cover plate 4 made of a transparent acrylic plate, and a watch 15. To the cover plate 4 is fixed a water nozzle 10 which in turn is attached to the bottom of the water bath 2 through guide tubes 6 and 23. Thus, an adhesive sheet 22, which is prepared by coating the both sides of a sample 20 of polyurethane with a pressure-sensitive adhesive 21, has its one side bearing a hook 9 and its other side bearing the cover plate 4. After a weight 9 is hanged from the hook 9, a small quantity of water is continuously poured from the nozzle 10 onto the sheet 20 thereby to humidify the adhered portion of the hook 9. Then, by the action of the gravity of the weight 12 and as a result of the deterioration in the adhesion due to the high moisture, the hook 9 leaves the cover plate 4 so that the drop of the weight 12 is detected by a switch 14 having a sensing arm 24. A watch 15, which has been started in response to the opening operation of the cock 5, is interrupted to indicate the moisture resistance of the sample 20.