A common rail housing for a common rail injection system is composed of a pressure accumulation pipe whose outer circumference is formed in complete round shape in cross section and which is provided inside with a pressure accumulation chamber having oval cross section and a plurality of blanch pipes each of which is provided inside with a fuel conduit bore. Outer circumference of the oval cross section has a specified portion whose curvature is smaller than that of complete round shape having an area equal to that of the oval cross section. Each of the blanch pipe is connected to the pressure accumulation pipe so that the fuel conduit bore and the pressure accumulation chamber intersect nearly perpendicularly to each other at the specified portion. Accordingly, when fuel is supplied to the pressure accumulation chamber, not only the stresses concentrated on the specified portion are limited but also wall strength of the pressure accumulation pipe at the specified portion is reinforced.