PURPOSE: To find magnetic domains and to produce a low iron-loss grain- oriented electrical steel sheet by forming a film of an infilterative body to the grain-oriented electrical steel sheet after finish annealing then subjecting the steel sheet to partial heat treatment at intervals to form the infiltrative body at intervals.

CONSTITUTION: The film of the infilterative body is formed to the grain-oriented electrical steel sheet subjected to finish annealing, then the steel sheet is subjected to the partial heating treatments at intervals to form the infiltered body, having the steel component or structure different from the component or structure of the matrix at intervals. The above-mentioned film of the infiltrative body is preferably formed over the entire surface of the steel sheet or at intervals. The magnetic domains are finely segmented without the loss of the effect of improving the iron loss, etc., even if the heat treatment such as stress relief annealing is executed by the above-mentioned method, by which the grain-oriented electrical steel sheet having extremely low iron loss is obtd.