PURPOSE: To keep constant the pressure of contact between wiping rubber and the surface of a windshield, by securing a cam on a vehicle body to turn the arm butt of a wiper through a cam lever to to adjust the force of an arm spring.

CONSTITUTION: Arms 3, 4 for supporting wiping rubber are pivotally connected by a pin 5 to an arm butt 2 secured on a wiper shaft 1. The arms 3, 4 are energized toward the surface of a windshield by an arm spring 6. A cam lever 7 is pivotally connected by a pin 8 to the arm butt 2. One end 7A of the cam lever 7 is located in contact with a cam 9 secured on a vehicle body. One end of the arm spring 6 is coupled to the other end 7B of the lever 7. With the turning of the arm butt 2, the end 7A of the lever 7 is moved along the surface 9A of the cam 9 so that the force of the spring 6 is varied.