A core for magnetic head, which has a surface roughness of not higher than 2 .mu.m in the side wall of a groove for defining the track width of the core, can be obtained by subjecting at least a portion, which defines the track width, of a gapped bar made of ferrite and having a coil turn hole and a magnetic gap, to a laser-induced etching under a condition that a laser light having a power of 50-1,100 mW and a focused beam diameter of not larger than 20 .mu.m is irradiated to at least the track width-defining portion at a scanning speed of 2-110 .mu.m/sec in a halogen gas- or halide gas-containing atmosphere kept to a gas pressure of 10-200 Torr.