Evaporative fuel emission control system

An evaporative fuel emission control system includes a canister (20) that adsorbs fuel vapor generated in a fuel tank (10), canister outgoing gas producing means (32) that causes canister outgoing gas to flow out of the canister, vapor condensing means (34, 44) for condensing the canister outgoing gas to provide a processed gas containing a higher concentration of fuel vapor than that of the canister outgoing gas, and a processed gas passage (42) through which the processed gas is fed to the fuel tank. The system is operable to restrict flow of the processed gas into the fuel tank when the fuel vapor concentration in the processed gas is lower than or is expected to be lower than a predetermined level.