A power supply device includes a battery circuit module group in which a plurality of battery circuit modules are connected in series via their output terminals. The power supply device further includes a control circuit configured to: output, at intervals of a certain time, a gate signal for turning on and off a first switching element and a second switching element of each battery circuit module to the battery circuit modules in the battery circuit module group; and select one of the battery circuit modules that receives an input of the gate signal to output a predetermined voltage from the power supply device.