PURPOSE: To make arrangement so that a pedestrian may be able to judge the degree of danger accurately even at the time of rainy weather and at the same time an accurate alarm sound may be able to be issued.

CONSTITUTION: An ON-OFF detecting means 3 to detect the ON-OFF of a wiper switch is connected to a processing circuit 4, and the processing circuit 4 is connected to an alarm sound generating means 6, and a volume regulating means 5 to regulate the volume of an alarm sound to be issued from the alarm sound generating means 6 on the basis of an ON signal from the ON-OFF detecting means 3 is furnished to the processing circuit 4.