An evaporated fuel processing device may comprise a canister, a control valve disposed on a purge passage and switching between a closed state being a state of closing the purge passage and an open state being a state of opening the purge passage, a pump disposed between the canister and the control valve, an acquiring unit acquiring a characteristic value related to a characteristic of the pump in a situation where the control valve is in the closed state and the pump pressurizes gas in the purge passage on a control valve side relative to the pump, and an estimating unit estimating a flow rate of the gas that the pump discharges to the purge passage on the control valve side when the control valve is in the open state, by using the acquired characteristic value.