PURPOSE: To decrease burden of calculation exerted on the microcomputer of a multiple cylinder engine by storing a presently remaining fuel quantity of an intake port per 1/n cycle in the case the number of cylinder is (n), and setting the remaining fuel quantity of the intake port before one cycle of each cylinder.

CONSTITUTION: A fuel vaporization rate β inside an intake port appearing between one intake stroke and the next intake stroke per one cylinder is set by a means M1. Adhesion rate of injected fuel X on an intake port inner wall is set by a means M2. A fuel injection quantity Gf is set by a means 3 in compliane with {(Qp/A/f)-x Mf(n)}/(1-X) (Qp; intake air quantity, A/f; target air-fuel ratio, Mf(n); remaining fuel quantity inside the intake port before one cycle in (n) cylinder engine). Then the present remaining fuel quantity Mf inside the intake port set by a means 4 is stored by a means 5 per 1/n cycle, and the remaining fuel quantity Mf(n) inside an intake port before one cycle is set.