PURPOSE: To put an automatic viper in appropriate wiping action by controlling current application to a wiper motor according to the amount of rainfall in addition to starting action upon the detection of raindrops.

CONSTITUTION: An automatic wiper is provided with a raindrop sensor 3 for detecting raindrops, and a pressure sensor 4 for detecting the amount of rainfall by the pressure. In the 'on' state of a detection signal Rs from the raindrop sensor 3, a current is applied to a viper motor 10 intermittently according to the grade of the value P based on a pressure detection signal Ps, or the current flowing quantity to the viper motor 10 is adjusted to the value corresponding to the value P. Wiping speed is thereby changed automatically according to the amount of rainfall, so that a driver can concentrate his whole mind only on driving, which proves to be extremely effective also from the viewpoint of safety.