To provide a fuel pressure fluctuation reduction device which can provide a high durability and reduce the assembly man-hour of a fuel supply system.

By building an accumulator 8 in a fuel filter 3 provided between a low pressure pump and a high pressure pump, the pressure fluctuation of a fuel transferred from the high pressure pump to the fuel filter 3 can be reduced. Therefore, the durability of the low pressure pump, fuel supply piping and the inner member of the fuel filter 3 can be ensured. As the accumulator 8 encloses an filling gas 82 in a space surrounded by a partition 81, a metal bellows 83 and a bottom member 84, a higher durability is ensured in comparison with a pulsation damper having a rubber diaphragm. As the fuel filter 3 builds in the accumulator 8, the number of parts of the fuel supply system can be reduced and the assembly of the fuel supply system is facilitated and an assembly man-hour can be reduced.