A fuel injector device achieves simplification, a low cost and ejected fuel atomization in a structure that ejects fuel with an ejector. The device includes a gas feeding passage 12 towards a gas inlet valve of an internal combustion engine, an ejector 30 ejecting fuel to the gas feeding passage, and an auxiliary air passage 40a for supplying air to a position near the ejector. The gas feeding passage 12 includes a venturi pipe portion 13 having a reduced passage area, with a fuel discharge port 32a of the ejector and an air discharge port 15a of the auxiliary air passage being disposed in theventuri pipe portion 13. According to this, on one hand, simplification of the structure, cost reduction, and the like can be achieved, and on the other hand, the atomization of the injected fuel canbe promoted.