To provide a fuel injection device capable of improving waterproof performance of the coil portion. A fuel injection device 1 includes a coil bobbin 51 disposed in a housing 70 and having a bobbin outer peripheral surface 51a that holds a coil 50 and a bobbin inner peripheral surface 51b that is a surface on an opposite side of the bobbin outer peripheral surface 51a, and a first outer peripheral surface 46a and a first outer peripheral surface 10b (guide portion) that come into contact with the bobbin inner peripheral surface 51b. A first space S1 and a second space S2 (internal space) are formed by the first outer peripheral surface 46a and the first outer peripheral surface 10b, and the bobbin inner peripheral surface 51b, and the first space S1 and the second space S2 communicate with a space filled with the connecting portion 80.