To reduce the dispersion of the material in the operation of steel making and hot rolling stages and to obtain a grain-oriented silicon steel sheet having stable magnetic properties by estimating the primary factor of the dispersion of the material caused by disturbance in the operation before decarburizing annealing, swiftly changing the annealing pattern in decarburizing annealing for a silicon steel slab having a specified compsn. based on a material model and executing treatment at a specified heating rate.

A silicon steel slab contg., by weight, 0.8 to 4.8% Si, ≤0.085% C, 0.01 to 0.065% acid soluble Al, ≤0.012% N, and the balance Fe is heated at ≤1280°C, is subjected to hot rolling and is subsequently subjected to cold rolling for one time or ≥two times including annealing to regulate its sheet thickness into the final one, which is subjected to decarburizing annealing and is thereafter subjected to finish annealing to obtain a grain-oriented silicon steel sheet, where, in the decarburizing annealing stage, it is heated at the average heating rate of 10 to 40°C/sec at least to 650°C and is then heated at a heating rate of ≥60°C/sec to a temp. calculated based on a material prediction model to regulate the average grain size in the primary recrystallized structure, and after that, nitriding treatment is executed.