PURPOSE: To minimize the number of secondary coil of a power transformer in order both to lighten the power transformer in weight and to prevent decrease in productivity of the transformer for an endoscope unit.

CONSTITUTION: A circuit 14 of patient side including a charge coupled device (CCD) 12 and an outlet circuit 16 are joined together through an isolation device 15. Secondary coils A and B which are formative members of a power transformer 20 are connected with a switching regulator group 18 and a switching regulator group 19, respectively. Various voltage powers adjusted by the switching regulators groups 18 and 19 are supplied to the circuit 14 and the circuit 16 individually corresponding to a prescribed voltage, thus eliminating the necessity for providing secondary coils in every required voltage.