A power supply unit for an aerosol generation device is provided. The power supply unit includes an internal power supply configured to hold power supplied to a heater configured to heat an aerosol source, a connector connectable to an external power supply, a controller configured to control power supply from the internal power supply to the heater, and a first transistor positioned on a first power supply path between the connector and a positive electrode of the internal power supply. A current from the connector is supplied to a source of the first transistor. A current from a drain of the first transistor is supplied to the positive electrode of the internal power supply. The controller controls a voltage of a gate of the first transistor to adjust power supplied from the external power supply to the internal power supply.