A first housing has a canister passage communicating a first interior with a canister. A second housing has an atmospheric passage communicating a second interior with an atmosphere. A switching valve is accommodated in the first housing to switch communication of the canister passage with selectively one of a pressure detection passage and the atmospheric passage. A switching valve bypass passage communicates the canister passage with the pressure detection passage and bypasses the switching valve. A partition member separates the first interior from the second interior and has a communication hole communicating the first interior with the second interior. A contact member is equipped to an end of the partition member and is in contact with at least one of the first housing and the second housing. The partition member forms a clearance with the first housing and the second housing.