A method of controlling a fuel injection of a diesel engine for performing a plurality of fuel injections to cause a plurality of combustions inside a cylinder in one combustion cycle, is provided, which includes performing, on compression stroke, the plurality of fuel injections at substantially constant injection intervals while increasing an injection amount as an in-cylinder oxygen concentration decreases, and performing, after the plurality of fuel injections, another fuel injection including a larger injection amount than in the plurality of fuel injections near a top dead center of the compression stroke.