AUXILIARY POWER SUPPLY DEVICE, POWER SUPPLY DEVICE, AND MEDICAL SYSTEM

An auxiliary power supply device in which an increase in the size of an entire system including both an auxiliary power supply circuit unit and a sub-power supply circuit unit is able to be curbed is provided. There is provided an auxiliary power supply device configured to be connected to a power supply device, the auxiliary power supply device including: an auxiliary power supply circuit unit configured to supply electric power to the power supply device in a case in which supply of electric power to the power supply device is shut off; and a sub-power supply circuit unit having an input side connected to the power supply device and an output side connected to a load and configured to supply an output voltage to other circuit units in accordance with electric power supplied from the power supply device.