PURPOSE:To simplify the operation of varying the set load on the wiper blade by a method wherein a tension member is applied to an inclined surface of a movable member and the load applied on an arm is varied through the tension member by the movement of the movable member. CONSTITUTION:A movable member 13 is attached to an arm head 4 in such a manner that the member 13 slides only in the longitudinal direction of the arm head 4 and the movement of the member 13 in that direction is effected by a cam 12. Further, the inclined surface 13e is formed on the upper surface of one end of the member 13 in such a manner that the surface 13e does not run parallel to the axis 3 of the wiper. In addition, arm retainers 15 are attached to the arm 5 so as to extend outwardly of one end of the arm 5 and the tension member 16 is supported by the retainers 15. The tension member 16 comprises a shaft 18 projecting downwardly from a case 17 and provided with a roller 18a at the top end thereof, a coil spring 19 arranged on the upper surface of the shaft 18 and a bolt 21 for adjusting the pressure of the spring 19 and the roller 18a of the shaft 18 is brought into pressure cntact with the inclined surface 13e of the movable member 13.