PURPOSE: To obtain the isolated voltage output circuit which is inexpensive and superior in safety and reliability by connecting plural parallel circuits, consisting of photocouplers and fixed resistances, to voltage adjusting circuits in series and bringing the respective photocouplers under the ON/OFF control of a control circuit.

CONSTITUTION: This output circuit consists of the control circuit 11 and voltage adjusting circuits 12 and 13, plural sets of the parallel circuits consisting of the photocouplers PC1 and PC2 or PC3 and PC4 and the fixed resistances R1 and R2 or R3 and R4 connected in parallel to them are connected in series to the voltage adjusting circuits 12 and 13, and the control circuit 11 perform the ON/OFF control over the respective photocouplers PC1-PC4 through 1st and 2nd control lines 11a and 11b. Here, when the photocouplers PC1-PC4 are turned ON or OFF through the 1st or 2nd control line 11a or 11b of the control circuit 11, the fixed resistances R1-R4 connected to them in parallel are connected or disconnected and the voltage is adjusted to various output voltages according to their combinations.