Provided in accordance with the present invention is a grain-oriented magnetic steel sheet which has a thickness of 0.30 mm or less, linear grooves formed therein at a rolling-direction interval in the range of 2-10 mm, a depth of the linear grooves of 10 [mu]m or more, and a forsterite coating film thickness on the bottom of the linear grooves of 0.3 [mu]m or more, and in which the rolling-direction tension imparted to the steel sheet by the forsterite coating film and by the tension coating is 10.0 MPa or more in total, and the proportion of the eddy-current loss in the iron loss (W17/50) of the steel sheet to which an alternating field of 1.7 T and 50 Hz is applied in the rolling direction is 65% or less. Thus, the base steel having linear grooves for magnetic-domain refinement is further reduced in iron loss. When used to assemble a real transformer, the grain-oriented magnetic steel sheet can have excellent low-iron-loss characteristics.