PURPOSE: To clearly show the time for replacement of a laser by measuring the continuous laser lighting time, updating the cumulative time every time the value becomes higher than a predetermined one, and indicating the time when the value exceeds the predetermined threshold.

CONSTITUTION: A non-volatile memory 1 to store up the cumulative laser lighting time is an electrically-writable EEPROM to hold the written value. A microprocessor (MPU) 2 to perform various sorts of processings includes a laser lifetime judgement part 2-1 to judge the laser lifetime. A counter 3 begins to measure the continuous laser lighting time as it receives a laser lighting signal (a) from a laser 4 and stops the measurement as it receives a laser lights- out signal (b). An indication LED 5 shows that the laser 4 is used as long as its lifetime when the laser is lighted for an as long time as its lifetime.