To provide a fuel injection device which injects two kinds of fuels and can part injection of the fuels.

The fuel injection device is provided with a nozzle body 11 which injects and feeds fluid concerning combustion to an internal combustion engine and in which a first nozzle hole 30 and a second nozzle hole 40 are formed; an outside needle 50 which switches the presence of injection of the fluid through the first injection hole by lift operation by accommodation able to reciprocate to the inside of a nozzle body; an inside needle 60 which switches the presence of the fluid through the second injection hole by lift operation by accommodation able to effect reciprocating movement to the inside of the outside needle; and flow paths 16 and 17 through which two kinds of fluids concerning combustion are separately guided to each of the first and second injection holes. Further, it is desirable that the flow paths are provided with the first flow path 16 which is formed in the first gap between the outer periphery of the outside needle and the inside periphery of the nozzle body and through which first fluid flows; and the second flow path 17 formed in a second gap between the outer periphery of the inside needle and the inner periphery of the outside needle and through which second fluid flows.