PURPOSE: To make the construction of the emission quantity control device of strobe simple and make the production cost thereof lower by changing the resistance value of a variable resistor constituting the distance detector in proportion to the square of the subject distance.

CONSTITUTION: A mechanical movement transmitting means 6 so drives a resistor 2 that the driving length of the resistor 2 of a variable resistor 4 is proportional to the square of the distance moving length of a lens barrel 5. Hence, the variable resistor 4 inputs the output proportional to the square of the distance moving length of the lens barrel 5 to an integrating circuit 9 through a buffer 7 and a logarithmic expanding diode 8. The integrating circuit 9 integrates this input and the input expressed by the function with F value and the output thereof is inputted to a comparator 10. The comparator 10 outputs the strobe emission stop signal when the output voltage of the integrating circuit 9 has become equal to a reference voltage. In this way, the need for providing separate square circuits is eliminated and the construction of the strobe emission quantity control device may be simplified.