A fuel vapor purge device includes a canister connected to an internal combustion engine and a fuel tank via a purge passage to adsorb and hold a part of fuel vapor, a switch valve connected to the canister and to an atmosphere, and a pump connected to the switch valve via a pump passage and to the atmosphere via an atmosphere passage. The pump is capable of depressurizing or pressurizing an interior of the fuel tank, and the switch valve switches connection of the canister between with the atmosphere and with the pump. The fuel vapor purge device further includes a seal valve provided in the pump passage to open or close the pump passage depending on a pressure in the atmosphere passage.