A pump characteristics expression of a pump is developed based on a closed-state pressure detected when the pump is driven while a space between a pump passage and a first passage is closed, an open-time pressure detected immediately after the space is opened while the pump is operated, and a flow rate characteristics expression of the pump passage. A reference pressure is determined by an intersection point between the pump characteristics expression of the pump and a flow rate characteristics expression of an orifice having a predetermined passage area. A leak check portion determines whether a leak of fuel evaporation generated from a fuel tank is within an allowable range by comparing the reference pressure and a pressure detected when the pump is operated for a predetermined period while the space is opened.