A fuel tank device of a vehicle includes a fuel supply pipe, a first fuel tank, a second fuel tank, and a resistance portion. The fuel supply pipe includes a main pipe, and a first branch pipe and a second branch pipe that branch from the main pipe. The first fuel tank is connected to the first branch pipe, the second fuel tank is connected to the second branch pipe, and the resistance portion is provided in the main pipe and is configured to impart resistance to liquid fuel flowing in the main pipe.