PURPOSE: To prevent permanent deformation and early deterioration of a wiper blade by energizing a wiper blade by utilizing the negative pressure at the time of engine operation, and preventing application of the pressing force to the wiper blade when the wiper is not used at the time of engine stop.

CONSTITUTION: An arm piece 5 for supporting a wiper blade is fitted at the tip end of a retainer 4 of a wiper arm 20, and an air piston 21 as an energizing means is fixed inside the retainer 4. A tube 49 communicating to pressure chambers 41, 42, 43 is connected to the air piston 21, and further communication- connected to an intake manifold 53 through a pressure regulating box 50, a release valve 51 and a check valve 52. Accordingly, when the intake manifold 53 becomes a negative pressure of a specified value at the time of engine operation, the pressure chambers 41, 42, 43 become a negative pressure state via the check valve 52 etc., so that the pressing force onto the wiping-surface side is applied to the retainer 4 and the wiper blade at the tip end of the arm piece 5 presses against the surface to be wiped.