Abstract: An engine rotational number controller includes an engine rotational number detector 5 for detecting the number of rotation of an engine, a throttle opening detector 7 for detecting a throttle opening of the engine, an ignition device 11, a stepping motor 15, an injector 16, and a control circuit 4 for delaying an ignition timing of the ignition device 11 when the number of rotation of the engine becomes higher than a predetermined upper limit in the case where the throttle number is constant and for opening a sub-throttle valve 14 of a throttle valve 12 by means of the stepping motor 15 to increase an amount of intake air and to increase an amount of injected fuel in the injector 16 when the number of rotation of the engine becomes lower than a predetermined lower limit in the case where the throttle opening is constant.