PURPOSE: To simplify a circuit for cost reduction by duty ratio controlling pulse signals from a triangular wave generator on the basis of running to control a fuel pump with these signals.

CONSTITUTION: When a signal is applied to the input of I/O20 from a running condition detecting means 11, CPU 21 computes an optimum rotational frequency for the running condition to apply voltage to a comparator 17 which generates pulse signals subjected to duty ratio control by triangular voltage and comparation voltage to control a transistor 13. A fuel pump driving circuit 24 controls current supplied to a fuel pump 23 on the basis of said signal. Thus, the fuel supply pump can be controlled by a simple circuit.