An apparatus for controlling the evaporated fuel of an internal combustion engine secures the working capacities of the canisters and properly controls an air-fuel ratio when resuming the purging of evaporated fuel into the engine.The apparatus has the first and second canisters for adsorbing evaporated fuel produced in a fuel tank. The canisters are connected in series between an atmospheric hole of the first canister and an intake duct of the engine. Air from the atmospheric hole passes through the canisters and releases the fuel adsorbed by the canisters. The air and released fuel are purged into the intake duct. During the operation of the engine, a path guides evaporated fuel from the fuel tank into an adsorption material disposed in the second canister, so that the fuel adsorption state of the adsorption material is substantially unchanged between a given purge operation and the next purge operation around a path for purging air and fuel from the second canister into the intake duct. The apparatus also has a fuel supply controller that uses the concentration of purged fuel of a first purge operation when calculating, at a second purge operation, a fuel injection quantity to achieve a target air-fuel ratio.