PURPOSE: To enable the detection of rainfall, by forming a rainfall detector on a heating member through an insulating layer.

CONSTITUTION: A weather state detecting apparatus is constituted of the insulating material 1B on a heating member 1A and comb shaped conductive patterns 1C, 1C' on the surface thereof and a switch for supplying power to the heater material 1A corresponding to the continuity of the patterns 1C, 1C' due to rain droplets is turned ON. In this case, a time required in evaporating rain droplets by the heating member 1A changes and the detection of rainfall can be also performed corresponding to the ON-time of the switch.