PURPOSE: To prevent a diaphragm from losing the function due to the partial breakage thereof while absorbing and reducing effectively the large pump pulsation with compact configuration.

CONSTITUTION: The upper end of the lower side connecting pipe 3 constituting a housing H is extended concentrically in a tubular diaphragm 1 to provide a guide wall 21. A spring member 4 for urging the diaphragm 1 inward is disposed in an outer space 1a of the diaphragm 1 and the outer space 1a is adapted to communicate to a fuel tank 5 through a through hole 32 provided in the housing H wall. When fuel has pulsation, the diaphragm 1 is deformed expansibly and contractively against the urging force of a spring member 4 to absorb and reduce the pulsation. The large pulsation is absorbed by the compact tubular diaphragm 1. Even if a portion of the diaphragm 1 is broken and fuel leaks into the outer space 1a, the fuel is returned through the through hole 32 to the fuel tank 5 and the elastic force of the diaphragm 1 is maintained by the spring member 4.