To recycle waste materials, the work is concerned with development of a glass-ceramic from a Korean incinerator fly ash with a high content of Cl. As a pre-treatment of ash, water washing the fly ash was used to remove the high Cl content before melting the ash. The process induced internal crystallization of fly ash after melting under a single stage heat treatment without adding nucleating agents into the ash. As a result, fracture stress of 220MPa and fracture toughness of 1.7 MPam(1/2) were found in the glass-ceramic, which were high values compared to others reported. Thus, the present process suggests that a good glass-ceramic produced from an incinerator ash could be applicable for structural materials in terms of economical and environmental points.