PURPOSE: To decrease length of a wiring cord, eliminate the necessity for a distributor, simplify constitution and facilitate assembly work, by insulating both positive and negative electrodes of a spark plug, providing a terminal to each electrode and wiring the plural spark plugs in series.

CONSTITUTION: A power transistor 3 is turned on and off in accordance with an ignition timing signal, accordingly a primary current in an ignition coil 2 is converted into a secondary side high voltage current and directly fed to spark plugs. The spark plugs 20aW20d provided in four cylinders perform a spark discharge simultaneously with input of the high voltage current. In this way, terminals 12a, 13a of the spark plugs 20 are connected in series to eliminate the necessity for using a distributor, accordingly a use amount of expensive high tension cables can be reduced. Further this ignition device can be directly applied to a stratified injection fuel engine and spark assisted Diesel engine.