A fuel vapor gas purge system comprising: a fuel tank accumulating a fuel; a canister adsorbing a vaporized fuel when a fuel vapor gas generated in the fuel tank is introduced into the canister, and being capable of desorbing the adsorbed vaporized fuel; a passage forming member forming an intake passage of an internal combustion engine, the internal combustion engine mixing and combusting the vaporized fuel desorbed from the canister and a combustion fuel; a purge pump pumping the vaporized fuel in the canister to the intake passage through a purge passage; a valve device including a valve element switchable between an allowed state in which the vaporized fuel is allowed to flow into the intake passage and a blocked state in which the flow of the vaporized fuel into the intake passage is blocked, the valve device being attached to the passage forming member and controlling a flow of the vaporized fuel pumped by the purge pump; an electric circuit disposed in the valve device and energized to generate a driving force to drive the valve element, the electric circuit being capable of driving the valve element into the blocked state by an urging force of a spring when the driving force is not generated or into the allowed state when the driving force is generated; and a switch portion (151, 221) including an electric contact portion that causes the electric circuit to be in a conductive state in which the electric circuit is closed when the valve device is attached to the passage forming member, and causes the electric circuit to be in a nonconductive state in which the electric circuit is open and the valve element is in the blocked state when the valve device is detached from the passage forming member. a fuel tank accumulating a fuel; a canister adsorbing a vaporized fuel when a fuel vapor gas generated in the fuel tank is introduced into the canister, and being capable of desorbing the adsorbed vaporized fuel; a passage forming member forming an intake passage of an internal combustion engine, the internal combustion engine mixing and combusting the vaporized fuel desorbed from the canister and a combustion fuel; a purge pump pumping the vaporized fuel in the canister to the intake passage through a purge passage; a valve device including a valve element switchable between an allowed state in which the vaporized fuel is allowed to flow into the intake passage and a blocked state in which the flow of the vaporized fuel into the intake passage is blocked, the valve device being attached to the passage forming member and controlling a flow of the vaporized fuel pumped by the purge pump; an electric circuit disposed in the valve device and energized to generate a driving force to drive the valve element, the electric circuit being capable of driving the valve element into the blocked state by an urging force of a spring when the driving force is not generated or into the allowed state when the driving force is generated; and a switch portion (151, 221) including an electric contact portion that causes the electric circuit to be in a conductive state in which the electric circuit is closed when the valve device is attached to the passage forming member, and causes the electric circuit to be in a nonconductive state in which the electric circuit is open and the valve element is in the blocked state when the valve device is detached from the passage forming member.