A compression self-ignition engine (1) performs a SI combustion in which an air-fuel mixture burns due to flame propagation by means of ignition of a spark plug (25), and a CI combustion in which the air-fuel mixture burns due to self-ignition caused by this flame propagation. An ECU (10) is equipped with a first control means that, on the basis of the operating state of the engine (1), controls a SI rate, as an index related to the percentage of the amount of heat generated by SI combustion with respect to the amount of heat generated by CI combustion or the total amount of heat generated by SI combustion and CI combustion, and a second control means that controls cylinder temperature prior to SI combustion. The combustion state of the SI combustion and the CI combustion is changed by means of the first and the second control means in accordance with the operating state of the engine (1) during one combustion cycle of the engine (1).