In a method of producing a grain-oriented electrical steel sheet by hot rolling a steel slab having a chemical composition including C: 0.001˜0.10 mass %, Si: 1.0˜5.0 mass %, Mn: 0.01˜0.5 mass %, S and/or Se: 0.01˜0.05 mass %, sol. Al: 0.003˜0.050 mass % and N: 0.0010˜0.020 mass %, subjecting to single cold rolling or two or more cold rollings including an intermediate annealing therebetween to a final thickness, performing primary recrystallization annealing, and thereafter applying an annealing separator to perform final annealing, a temperature range of 550° C. to 700° C. in a heating process of the primary recrystallization annealing is rapidly heated at an average heating rate of 40˜200° C./s, while any temperature zone of from 250° C. to 550° C. is kept at a heating rate of not more than 10° C./s for 1˜10 seconds, whereby the refining of secondary recrystallized grains is attained and grain-oriented electrical steel sheets are stably obtained with a low iron loss.