A window glass apparatus includes a heater for heating a part of a windshield which is a particular part of a window glass of a host vehicle, and a control ECU configured to control an amount of the electric power supplied to the heater. The control ECU detects a preceding vehicle and controls the amount of the electric power supplied to the heater in such a manner that the amount of the electric power supplied to the heater is reduced as compared with a case where the preceding vehicle is not detected, using information on the detected preceding vehicle.