To provide a power source apparatus constituted so as to take out the output of a plurality of batteries having different output characteristics through common terminals and to suppress the decrease of the energy efficiency due to the connection between the batteries as much as possible.

The plurality of the batteries 10a to 10c having different output voltages and output currents are connected so that the outputs of the batteries are outputted to the terminals 4, 5 so as to satisfy the relation of parallel connection after the output is regulated to the same output voltage. Since the output of the batteries are output in parallel, there is no inconvenience of limiting the output current of the entire power source of the batteries having small output currents different from a series connection. Since the output is regulated to the same output and connected, a problem such as a reverse current or the like does not occur. When this is applied to a tandem solar cell, light absorption wavelength characteristics can be allocated so as to utilize the solar light to the maximum efficiency, and even when the wavelength distribution of the solar light is largely deviated from the standard distribution, the photoelectric energy conversion efficiency is not lowered.