A detecting unit that detects a specific pressure difference between a pressure of gas that has passed throuch a canister and a pump and a pressure of the gas before passing through the canister and the pump. A gas flow rate from the pump may be higher with a smaller pressure difference between upstream and downstream sides relative to the pump, and higher with a higher purge gas density. A gas flow rate from the canister may be lower with a smaller pressure difference between upstream and downstream sides relative to the canister, and lower with a higher purge gas density. An estimating unit may estimate a flow rate of the purge gas while the specific pressure difference is an unchanged pressure difference being a pressure at which the flow rate of the gas is not chanced by the density of the purge gas.

A detecting unit that detects a specific pressure difference between a pressure of gas that has passed throuch a canister and a pump and a pressure of the gas before passing through the canister and the pump. A gas flow rate from the pump may be higher with a smaller pressure difference between upstream and downstream sides relative to the pump, and higher with a higher purge gas density. A gas flow rate from the canister may be lower with a smaller pressure difference between upstream and downstream sides relative to the canister, and lower with a higher purge gas density. An estimating unit may estimate a flow rate of the purge gas while the specific pressure difference is an unchanged pressure difference being a pressure at which the flow rate of the gas is not chanced by the density of the purge gas.

A detecting unit that detects a specific pressure difference between a pressure of gas that has passed throuch a canister and a pump and a pressure of the gas before passing through the canister and the pump. A gas flow rate from the pump may be higher with a smaller pressure difference between upstream and downstream sides relative to the pump, and higher with a higher purge gas densiy. A gas flow rate from the canister may be lower with a smaller pressure difference between upstream and downstream sides relative to the canister, and lower with a higher purge gas density. An estimating unit may estimate a flow rate of the purge gas while the specific pressure difference is an unchanged pressure difference being a pressure at which the flow rate of the gas is not chanced by the density of the purge gas.

A detecting unit that detects a specific pressure difference between a pressure of gas that has passed throuch a canister and a pump and a pressure of the gas before passing through the canister and the pump. A gas flow rate from the pump may be higher with a smaller pressure difference between upstream and downstream sides relative to the pump, and higher with a higher purge gas densiy. A gas flow rate from the canister may be lower with a smaller pressure difference between upstream and downstream sides relative to the canister, and lower with a higher purge gas density. An estimating unit may estimate a flow rate of the purge gas while the specific pressure difference is an unchanged pressure difference being a pressure at which the flow rate of the gas is not chanced by the density of the purge gas.