FUEL VAPOR PROCESSING DEVICE

PROBLEM TO BE SOLVED: To close the atmosphere valve of a canister forcedly to close the inside of the device and realize a proper diagnosis based on the pressure intro duced in a device, at the air tightness diagnosis time of a processing device. SOLUTION: A canister 13 collects a fuel vapor generated in a tank 1 through a line 21 and the fuel is purged to an intake passage 31 through the line 30 as occasion demands. Both members 1, 13 form one closed space mutually. A atmosphere valve 35 provided in the atmosphere hole 38 of the canister 13 includes pressure rooms 35c, 35d divided by a diaphragm. In the pressure room 35c, the inner pressure of the canister 13 is introduced and the pressure room 35d has a pressure port 35e for introducing an outer pressure. A control valve 32 closes a purge line 30. A pipe 42 connects two pressure ports 35e, 41. The pressure for diagnosing is introduced in an introducing port 43 provided on a pipe 42. A check valve 44 provided on the pipe 42 between both ports 43, 41 allows the introduction of the pressure from the introduction port 43 to the pressure port 41.