Provided is a power system that can arbitrarily set output power while stabilizing output voltages. Connection terminals 13 and 23 of lower power sources 1 and 2 are connected to external connection terminals 41 in parallel. Voltage measurement section 31 measures voltage values of external connection terminals 41 as measured voltage values. Power converters 12 and 22 measure power supply capacities of lower power sources 1 and 2, respectively. Output instruction section 32 adjusts power or currents flowing through connection terminals 13 and 23 based on the measured voltage values and the power supply capacities so that the measured voltage values are included in a predetermined voltage range.