PURPOSE: To advance, delay or keep the ignition timing at a predetermined angle selectively according to a fixed crank angle, by producing an ignition pulse at the time instant when a period left after subtracting a predetermined time from the fixed crank angle is passed from a reference position.

CONSTITUTION: The time period left after subtracting a predetermined time, i.e., time leg T from ignition to combustion from a fixed crank angle θA is calculated, and an ignition pulse is produced at the time instant when the above period is passed from a reference position B. Here, providing that the speed of rotation of a crank angle is F, a constant time component T1 and the above- mentioned time lag T satisfy the following relationship: T=T1+(θB-θA)× 103/(6×F), where θB is the advance angle of the ignition timing at the reference position B. Therefore, if θB=θA, the fixed angle component is zero. If θB>θA, the fixed angle component is added to the constant time component T1. Further, if θB<θA, the former is subtracted from the latter. With such an arrangement, it is enabled to control the ignition timing in a desired manner.