A magnetic domain refining treatment is performed by dividing a surface of a steel sheet into a plurality of regions in a widthwise direction, disposing a laser irradiation apparatus or an electron beam irradiation apparatus in each of the regions, and forming beam-irradiated regions through beam irradiation, wherein beams are irradiated so that a nature of a juncture between beam-irradiated regions satisfies 0≤α≤0.3×a and −1.2×a+0.02×w−0.5×α−6.5≤β≤−0.13×a−200×(1/w)+5.4 when TD spacing β at the juncture between the beam-irradiated regions is −3 to 0 mm, whereby a grain oriented electrical steel sheet having an excellent iron loss property is produced in a good productivity.