Fuel injection control device

A fuel injection control device in which fuel injected into the combustion chamber (10) is ignited after a pre-mixing period has elapsed following the completion of the injection of the fuel, includes target pre-mixing period determining unit for determining the target pre-mixing period on the basis of the engine operating conditions , actual pre-mixing period detection unit for detecting the actual pre-mixing period, and pre-mixing period adjustment means for adjusting the pre-mixing period of the fuel so that the actual pre-mixing period approaches the target pre-mixing period. With this device, the pre-mixing period of the fuel can be appropriately controlled, and the exhaust gas can be reliably improved.