The purpose of the invention is to improve accuracy of an auto choke controller without increasing a cost. When engine speed detected by an engine speed detection sensor 49 is above a set engine speed, energizing time to a PTC type heater 42 to be a heater for auto choke is made to be performed by a pulse control of a transistor 47 by a microcomputer 46, external resistance for regulating voltageto the heater for auto choke conventionally used can be unnecessitated. When the auto choke is applied to an engine of a different characteristics, the application can be easily coped by changing an on-pulse width in the microcomputer 46 according to the characteristics of an applied engine.