To provide a fuel supply device of an internal combustion engine capable of efficiently and satisfactorily heating a fuel and reliably supplying the satisfactorily heated fuel even with a simple structure.

In the fuel supply device 1, a fuel rail 2 has a fuel circulating part 21 and a fuel stay part 22. A heating member 3 is disposed so that a heating surface 30 may face to the fuel stay part 22. A partition part 25 is provided between the fuel circulating part 21 and the fuel stay part 22. A partitioning wall part 26 is provided in the fuel stay part 22. The fuel stay part 22 has a contact passage 28 formed between the heating surface 30 of the heating member 3 and the partitioning wall part 26 and a communication passage 27 formed between the partitioning wall part 26 and the partition part 25. A partition communication part 252 and a partitioning wall communication part 261 are provided in the partition part 25 and the partitioning wall part 26, respectively. The contact passage 28 is connected to a fuel suction port 411 of a fuel supply passage 41 supplying fuel to a fuel injection valve 4.