To provide a low iron loss grain-oriented magnetic steel sheet with which the iron loss characteristic is drastically improved in comparison with the conventional steel sheet by using a means except the conventional groove and strain-formation and further, reducing the eddy current loss while restraining the increase of the hysteresis loss.

The low iron loss grain-oriented magnetic steel sheet contains metal or metal compound, which has the grooves at one position or the plurality of positions in either one side or both sides of the steel sheet on the front and back layers and the magnetic anisotropic constant is two or more times of the magnetic anisotropic constant of Fe in the width directional range of ≥4μm from the one-side surface or both-side surfaces of the groove side surfaces and in the thick directional range of ≥0.75 times of the groove depth from the steel sheet surface, and which has at least one of an axis of easy magnetization in the direction having the angle within ±12° to the normal line direction of the groove side surface.