PURPOSE: To provide a protective circuit for a pulse laser driver for controlling an output of a charge pulse to prevent an erroneous operation of a pulse generator at the time of an unexpected power source voltage drop or turning ON/OFF of a switch.

CONSTITUTION: A circuit for so controlling that a charge pulse generator 6 does not output a charge pulse in the case of an excess variation in a power source voltage is provided between a power source 5 and the generator 6 for generating the pulse to be output to a pulse laser driver. The protective circuit for the driver comprises a comparator 2 connected at its positive input terminal to the power source 5, a low-pass filter 1 connected between a negative input terminal of the comparator 2 and the power source 5, a latch circuit 3 connected to the output terminal of the comparator 2, and an AND logic gate 4 connected with the circuit 3 and the generator 6 to output a charge pulse.