To provide an excellent adhesive property with a human bone when a stem assembly is embedded in the human bone to be fixed for a long period by fixing a stem part comprising a sintered body or hardened body of a calcium phosphate compound in such a way that an outer surface of it is exposed from a stem to a stem part containing and fixing part.

A stem assembly 20 comprises a stem 22 of metal material such as titanium, and a plate shaped stem part 23 comprising a separate member from the stem 22 as a sintered body or hardened body of a calcium phosphate compound to be fixed to the stem 22. In an embedded part 22a of the stem 22, bottomed parts 24 are formed on both side surfaces for containing and fixing the stem parts 23. The plate-shaped stem part 23 and the bottomed recess part 24 have almost similar plane form and thickness (depth), so by fitting the stem parts 23 into the bottomed recess parts 24, the stem assembly 20 composes a smooth surface as a whole. The stem parts 23 are fixed to the bottomed recess parts 24 using an adhesive.