PURPOSE: To aim at the promotion of checking an unnecessary waste of power, by installing a discharge energy control circuit which controls energy in an inductive discharge part on the basis of an engine driving state signal, while controlling the inductive discharge duration.

CONSTITUTION: When a contact breaker 10 opens, the current of a power source 1 flows into a condenser 125, causing terminal voltage Vc to go up, and when the voltage exceeds a threshold value BES, a transistor 126 is turned on whereby part of the current has a transistor 9 conducted, compulsorily conducting a power transistor 5 and feeding an ignition coil 1 with a primary current. At this time, if a secondary discharge current flows therein, this current is forcibly made to be zero. Like this, the inductive discharge current is pulled back to zero by compulsion with times t2 and t3 according to a state of engine operation and discharge energy is varied without waiting a time when the inductive discharge current is automatically returned to zero.