To obtain an excellent mechanical strength such as rigidity of a part to which another component is fitted without requirement of fitting a fixing part for fixing another component by post-working.

A hollow platy body P having a fitting hole is equipped with one side wall 1 and the other side wall 2 opposed at an interval to each other. Peripheral fringe parts of both are blockaded with end walls 3. Mutually crossed platy inner ribs 4 are formed integrally with both walls 1, 2 between one side wall 1 and the other side wall 2. A fitting hole 5 for fitting another component open to the other side wall 2 is integrally formed at a part wherein the inner ribs 4 intersect each other. The fitting hole 5 is composed of an axial hole 5a for inserting an axial component or the like of another component, and a plurality of groove parts 5b radially cut in toward outsides in the inner ribs 4 from an inner peripheral surface of the axial hole 5a.