A fuel injection control apparatus of a four cycle engine having three cylinders (11a, 11b, 11c), comprising: a crank angle detection device for detecting crank angles of the four cycle engine; and a computation unit for computing a quantity of fuel injected in each stroke at a predetermined computation timing for each of the three cylinders, characterized in that the computation unit comprises: a first computation device for computing a quantity of fuel, which is injected when a cylinder of the three cylinders (11a, 11b, 11c) is in a compression stroke of a four stroke cycle, at a first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an intake stroke of the four stroke cycle; a second computation device for computing a quantity of fuel, which is injected in an intake stroke being one stroke before the compression stroke, at a second computation timing 240 degrees ahead of the crank angle of the first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an exhaust stroke of the four stroke cycle; and a third computation device for computing a quantity of fuel, which is injected in an exhaust stroke being two strokes before the compression stroke, at a third computation timing 240 degrees ahead of the crank angle of the second computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an expansion stroke of the four strike cycle. a crank angle detection device for detecting crank angles of the four cycle engine; and a computation unit for computing a quantity of fuel injected in each stroke at a predetermined computation timing for each of the three cylinders, characterized in that the computation unit comprises: a first computation device for computing a quantity of fuel, which is injected when a cylinder of the three cylinders (11a, 11b, 11c) is in a compression stroke of a four stroke cycle, at a first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an intake stroke of the four stroke cycle; a second computation device for computing a quantity of fuel, which is injected in an intake stroke being one stroke before the compression stroke, at a second computation timing 240 degrees ahead of the crank angle of the first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an exhaust stroke of the four stroke cycle; and a third computation device for computing a quantity of fuel, which is injected in an exhaust stroke being two strokes before the compression stroke, at a third computation timing 240 degrees ahead of the crank angle of the second computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an expansion stroke of the four strike cycle. a first computation device for computing a quantity of fuel, which is injected when a cylinder of the three cylinders (11a, 11b, 11c) is in a compression stroke of a four stroke cycle, at a first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an intake stroke of the four stroke cycle; a second computation device for computing a quantity of fuel, which is injected in an intake stroke being one stroke before the compression stroke, at a second computation timing 240 degrees ahead of the crank angle of the first computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an exhaust stroke of the four stroke cycle; and a third computation device for computing a quantity of fuel, which is injected in an exhaust stroke being two strokes before the compression stroke, at a third computation timing 240 degrees ahead of the crank angle of the second computation timing, when the cylinder of the three cylinders (11a, 11b, 11c) is in an expansion stroke of the four strike cycle.