PURPOSE: To provide a crystallized glass for magnetic head substrates, having a high thermal expansion coefficient adapted to a metallic magnetic substance such as sendust and good in cutting machinability.

CONSTITUTION: This crystallized glass for magnetic head substrates comprises 55-70wt.% SiO2, 10-20wt.% MgO, 4-20wt.% K2O, 0.1-5-wt.% P2O5, 0.1-5wt.% ZrO2, 0-3wt.% TiO2, 0-3wt.% Na2O, 0-3-wt.% ZnO and 2-10wt.% F2, contains α-cristobalite and/or α-tridymite and mica as a principal crystal phase and has 90-180×10-7/°C thermal expansion coefficient at 30-500°C.