A grain-oriented electrical steel sheet with extremely excellent magnetic properties by removing an etching resist coating well to form narrow grooves on a metal strip surface even with low-output laser, while reducing thermal effects on the metal strip caused by laser irradiation, and a method for forming grooves on a metal strip surface, having forming an etching resist coating with 0 to 70 lightness L* on at least one side of the metal strip, irradiating laser with less than 1.5 kW output on the etching resist coating while scanning the laser in a direction that intersects a rolling direction of the metal strip to remove a portion of the etching resist coating irradiated by the laser, and etching a portion of the metal strip below the removed portion of the etching resist coating to form grooves, the lightness L* being a L* value in a CIELAB color space (CIE1976L*a*b* color space).