A fuel injection controller for an internal combustion engine. The engine includes a fuel vapor treatment device having a collector for collecting fuel vapor generating in a fuel tank; a purge line that introduces purge gas into an intake passage of the engine, the purge gas being a mixture of fuel vapor released from the collector and air; and a purge valve provided in the purge line to adjust flow rate of the purge gas. The fuel injection controller corrects an amount of fuel injected from an fuel injection valve based on an amount of fuel vapor contained in the purge gas flowing into a combustion chamber of the engine. The fuel injection controller comprises an estimation section for estimating the inflow amount of the purge gas flowing into the combustion chamber based on a passed amount of purge gas that has passed through the purge valve and a compensation value for compensating transportation delay. The compensation value is set based on internal pressure of the intake passage and velocity of intake air that flows into the combustion chamber.