To provide a fuel injection device improving engine starting performance at the time of low temperature, such as preventing the occurrence of unexpected rotation drop in idle rotation state and obtaining a stable idling state and acceleration with good response.

The fuel injection device comprises an injection body 10 formed with an intake passage 10A communicating an intake path 24 on an intake port side and an intake path 22 on an air cleaner side, a throttle valve 42 freely opening/closing the intake passage 10A, and a fuel injection pump 15 jetting to a downstream side in an intake air flowing direction to the throttle valve 42 in the intake passage 10A. A bypass path 45 causing short-circuit between an upstream side and the downstream side in the intake air flowing direction to the throttle valve 42 in the intake passage 10A is provided, and a switch valve 46 freely opening/closing the bypass path 45 is equipped.