PURPOSE:To increase hardening speed and to simplify work by blending ammonium prim. phosphate and/or ammonium sec. phosphate with magnesium oxide as fixing components to prepare an asbestos fixing agent. CONSTITUTION:An asbestos fixing agent is prepd. by blending 100 pts.wt. ammonium prim. phosphate and/or ammonium sec. phosphate with 10-500 pts.wt. magnesium oxide, and 10-1000 pts.wt. of the asbestos fixing agent are added to 100 pts.wt. asbestos or asbestos-contg. material to fix the asbestos. The pref. grain size of the phosphates is 1-100mum. Unlike cement used as a fixing agent the asbestos fixing agent does not release alkali and is neutral and stable over a long period.