A fuel injection control device of an internal combustion engine capable of using multiple kinds of fuel includes an ECU with a ROM for storing multiple reference fuel injection quantity maps corresponding to mixture concentrations of the multiple kinds of fuels. A control program of the CPU stores which of the multiple reference fuel injection quantity map is used out of the maps in an EEP-ROM, performs starting control of an engine using the reference fuel injection quantity map which is used immediately before stopping previous time at the time of initiating the starting based on the stored maps and, at the same time, performs the starting control by gradually increasing the fuel injection quantity until the starting of an engine is finished. As a result, control of fuel supply is optimized in response to mixing different kinds of fuels, and the engine starting time is shortened.