A canister for a fuel vapor processor connected to a fuel tank and an engine includes a housing defining an adsorption chamber therein and an absorber being capable of adsorbing fuel vapor and filled in the adsorption chamber. The housing has an air communicating pipe communicating the adsorption chamber with the atmosphere, an introducing pipe communicating the adsorption chamber with the fuel tank and an exhaust pipe communicating the adsorption chamber with the engine. It is configured that airflow resistance in the canister along a first route between the air communicating pipe and the exhaust pipe is smaller than airflow resistance along a second route between the introducing pipe and the exhaust pipe.