To provided a method of forming a fuel supply passage in a fuel injection device capable of conquering difficulty and non-efficiency in production while lowering a wet surface temperature inside the fuel supply passage of the fuel injection device to enhance turbine efficiency.

An annular clearance is formed between an inner face of a fuel supply hole 24 and an outer circumferential face of a rod 26, in form structure formed in the cylindrical solid rod 26. A fuel velocity and a convection heat transfer coefficient are increased without changing an assigned fuel flow ratio and fuel temperature, to lower advantageously the local wet surface temperature inside the fuel supply hole 24 of relatively large diameter. Heat flow-out from a fuel nozzle increases compared with that in the fuel supply passage of typical small diameter, by increasing a wet surface area assigned by the fuel supply hole 24 of relatively large diameter. Local cooling is enhanced thereby to lower the local wet surface temperature inside the fuel supply hole.