PURPOSE: To prevent a lamp on a vehicle from sudden turning-off due to aging by providing a gate means for passing a reference signal while the turning-on of said lamp is detected and integrally recording the lighting time of lamp on the basis of passing reference signal.
CONSTITUTION: When a main lamp 1a is lit, a head lamp lighting time indicator 5 detects that lighting and sends the signal to a gate controlling section 513. Then, this section 513 passes the reference signal supplied through a reference signal generator 515 and sends it to a main lamp lighting time measurement control section 516. And this control section 516 measures and stores the input time of reference signal and sends the integrating time to an indication control section 518 to indicate the integrated lighting time on a main lighting time indicator 520. Thus, a driver can be informed of the life time of lamp on a vehicle, so that the early exchange of said lamp is urged to prevent the lamp from sudden turning-off.