A semiconductor device includes a voltage measurement unit that measures an output voltage of a battery and a voltage on a power supply path between the battery and an internal circuit supplied with electric power from the battery, a current measurement unit that measures a discharge current of the battery, and a control unit that calculates a theoretical value of the output voltage in a normal measurement mode assuming that the discharge current measured in a large current measurement mode is a maximum available current of the battery in the large current measurement mode, and calculates an amount of maximum available power of the battery in the large current measurement mode based on the calculated theoretical value of the output voltage and the voltage on the power supply path measured in the large current measurement mode.