Mechanical destruction of acicular asbestos has been carried out as a process for decontamination. The dehydration reaction of asbestos occurred at 600°C and has been completed for 2 h at that temperature. This dehydration reaction of asbestos led to weakening of the mechanical properties of asbestos. After grinding, the microstructure of asbestos appeared no acicular shape. Further, this technique could be applied to asbestos-containing cement board. The spent cement board has about 10-20 mass% of asbestos (chrysotile: Mg3Si2O5(OH)4) and 5 mm thickness was used. After heating at 600°C for 2 h and grinding, the microstructure of the sample also appeared no acicular shape. Thus it was cleared that heating at 600°C and then grinding treatment for asbestos (chrysotile) has a grate important effect of mechanical and chemical destruction of asbestos in both cases of free asbestos and asbestos-containing cement board.