A grain oriented electrical steel sheet keeps iron loss at a low level when assembled as an actual transformer and has excellent iron loss properties as an actual transformer, in which a film thickness a1 (μm) of insulating coating at the floors of linear grooves, a film thickness a2 (μm) of the insulating coating on a surface of the steel sheet at portions other than the linear grooves, and a depth a3 (μm) of the linear grooves are controlled to satisfy formulas (1) and (2): 0.3 μm≦a2≦3.5 μm  (1), and a2+a3−a1≦15 μm  (2).