An air source device includes: a tank; a compressor; an intake valve; and an ECU configured to acquire an intake amount, which is an amount of air sucked from an outside and supplied to the tank by the compressor, based on an increasing amount of a tank pressure, which is a pressure of the air accommodated in the tank, the increasing amount being an increasing amount from a time point when the intake valve is estimated to be changed from a closed state to an opened state.