PURPOSE: To permit the time of intermittence to be varied automatically according to the increase and decrease of the amount of rain drop and the wind velocity and secure a comfortable front visual range at all times by installing a wind- velocity detector on the captioned apparatus and setting the time of intermittence according to the amount of rainfall through manual setting.

CONSTITUTION: When the variable resistance 23 of a manual setting means C is increased, the potential at D point decreases, and also the base voltage of a transistor 11 decreases, so the current between emitter and collector increases, and a condenser 13 is charged with the higher charging speed than the preceding stage. Therefore, the cycle timing of the timing circuit C which controls ON/ OFF of the relay coil 21 of a driving means (d) is shortened. When the relative wind speed a car increases, the resistance of a strain gauge 8 in a wind-velocity detector 8 is increased by the positive pressure due to the wind speed, and the potential at D point, namely the potential of the base voltage of the transistor 11 decreases. When the base potential decreases, the cycle of timing of the timing circuit C is shortened likewise in case of manual operation.