Addition effects of some fluorides, NaF, MgF₂, CaF₂ and AIF₃, on the densification and the mechanical properties (Bending strength, fracture toughness) of hydroxyapatite were investigated. Sintering treatments were performed by hot-pressing under 10 min-20 MPa. An addition amount of each fluoride was fixed at 2.5 wt%. Of above fluorides added, calcium fluoride brought on extremely good results for the sintering of hydroxyapatite. The sintered compacts having relative densities more than 98% were obtained from 900°C in the case of adding calcium fluoride. On the other hand, the hydroxyapatite single compacts were fully densified above 1200°C. Moreover, the hydroxyapatite compacts containing calcium fluoride had a little higher bending strengths and fracture toughnesses than the hydroxyapatite single compacts because of the difference of their fine structures or grain sizes. Addition of other fluorides, on the contrary, obstructed the densification of hydroxyapatite.