Reservoir union for a hydraulic master cylinder of a vehicle

A reservoir union (1) for a hydraulic master cylinder of a vehicle for providing fluid stored in a reservoir to a master cylinder comprising a body connecting pipe (4) projected and provided on a lower side of a reservoir union body (1c) so as to connect with an union connecting boss (2b) projected and provided on an upper side of a cylinder body (2a) of the master cylinder (2) and a hose connecting pipe (5) projected and provided on an upper side of the reservoir union body (1c) so as to connect with a hose connected with the reservoir storing the fluid characterized in that a fluid storing chamber (10) communicating with the body connecting pipe (4) and the hose connecting pipe (5) is formed in the reservoir union body (1c).