To provide a multiple I/O power converter which can reduce the size and weight of a DC-DC converter, and to provide a fuel cell.

The multiple I/O power converter 1 comprises a plurality of step-up/down DC-DC converters A and B (power conversion circuits) having at least two I/O sections 3 and performing any one operation of step-up, step-down, regeneration or conduction when a plurality of coils L1 and L2 and a plurality of capacitors C1 and C2 function selectively by switching the switches G1-G8 in accordance with a preset operation mode. The plurality of power conversion circuits share the capacitors C1 and C2.