To surely avoid the worst situation of fuel leakage due to simultaneous occurrence of breakage of a canister, and restoring of a tank to a nearly original shape after the fuel tank is collapsed by impact load.

A dust capturing device 8 disposed between a leakage prevention valve 10 for blocking a ventilation passage 3, and an external device 2 in the ventilation passage 3 communicating between an internal space 1a of a fuel tank 1 and the external device 2, includes a valve member 9 having a filtering function, opened when the fluid flows toward the external device 2 from the internal space 1a of the fuel tank 1 through the ventilation passage 3 so that the dust mixed in the fluid cannot be captured, and switched from the opening state to a closing state when the fluid flows toward the internal space 1a from the external device 2 through the fluid passage 3 so that the dust mixed in the fluid can be captured.