The invention provides a distribution reservoir capable of alleviating the stress concentration to the water pressure, and wall plate parts (11) are joined with a high bonding strength to keep pressure resistance of sidewalls. A wall plate (15) of a bonding block part (2) is arc-shaped to suppress the stress concentration against a load from the inner side, when surfaces of strut members (12) are backing members and a space (S) of a flat flange portion (16) is a groove, the flat flange portion (16) of each wall plate part (11) is welded on the strut members (12), and the wall plate parts (11) are welded together with sufficient bonding strength.
