An engine start ignition circuit including a voltage booster for an engine generator which is an engine ignition apparatus of the full transistor igniter method, the engine start ignition circuit comprises: a generator which can be driven by the kick method, a voltage adjusting device connected to the generator for adjusting a voltage of power supplied from the generator, an electronic device connected to the voltage adjusting device for controlling ignition/operation control of the engine by voltage supplied from the voltage adjusting device, and an active boosting circuit connected between the voltage adjusting device and the electronic device, for boosting the output voltage of the voltage adjusting device to a predetermined nominal voltage of the electronic device upon the engine start by kicking the generator when the power supply is lower than the predetermined engine stationary operation, and stopping the boosting operation when the output voltage from the voltage adjusting device has become the predetermined nominal voltage of the engine stationary operation, wherein said active boosting circuit further includes a capacitor for charging electromotive force at least by said kick, wherein said active boosting circuit is a DC/DC converter having a feedback circuit for performing feedback so that the voltage of the output side becomes the predetermined nominal voltage, wherein said capacitor is inserted between said feedback circuit and said output side, characterised in that said active boosting circuit further comprises a bypass circuit for bypassing from the generator side to the load side of the active boosting circuit, and wherein the feedback circuit stops boosting operation of the DC/DC converter when a voltage V1 of the generator side bypassed to the load side of the DC/DC converter, which is reduced by a voltage drop of the bypass circuit, exceeds a predetermined nominal voltage V2 (V1 - voltage drop of bypass circuit > V2). a generator which can be driven by the kick method, a voltage adjusting device connected to the generator for adjusting a voltage of power supplied from the generator, an electronic device connected to the voltage adjusting device for controlling ignition/operation control of the engine by voltage supplied from the voltage adjusting device, and an active boosting circuit connected between the voltage adjusting device and the electronic device, for boosting the output voltage of the voltage adjusting device to a predetermined nominal voltage of the electronic device upon the engine start by kicking the generator when the power supply is lower than the predetermined engine stationary operation, and stopping the boosting operation when the output voltage from the voltage adjusting device has become the predetermined nominal voltage of the engine stationary operation, wherein said active boosting circuit further includes a capacitor for charging electromotive force at least by said kick, wherein said active boosting circuit is a DC/DC converter having a feedback circuit for performing feedback so that the voltage of the output side becomes the predetermined nominal voltage, wherein said capacitor is inserted between said feedback circuit and said output side, characterised in that said active boosting circuit further comprises a bypass circuit for bypassing from the generator side to the load side of the active boosting circuit, and wherein the feedback circuit stops boosting operation of the DC/DC converter when a voltage V1 of the generator side bypassed to the load side of the DC/DC converter, which is reduced by a voltage drop of the bypass circuit, exceeds a predetermined nominal voltage V2 (V1 - voltage drop of bypass circuit > V2).