LEAK DIAGNOSIS DEVICE OF FUEL VAPOR TREATMENT APPARATUS

A leak diagnosis device for a fuel vapor treatment apparatus, comprising: a first diagnosis unit that performs a leak diagnosis of a fuel tank based on a tank internal pressure in a closed state of a sealing valve; a determination unit that opens a sealing valve in a state where a purge valve and a switching valve are closed when the tank internal pressure is within a normal range, and determines whether there is an influence on the valve openability of the switching valve; and a second diagnosis unit that performs a leak diagnosis of the canister based on the tank internal pressure or the canister internal pressure when the determination unit makes a negative determination, and performs a leak diagnosis of the canister based on the canister internal pressure after closing the closed valve when the determination unit makes an affirmative determination.