To provide an apparatus and method whereby the precision of predefined line widths and repeating pitches are maintained, enabling a prescribed pattern to be machined.

The apparatus and method are provided with: a sheet material conveying part 2 for conveying a sheet material 10; a holding part 24 for holding the sheet material 10; a laser irradiation part 35 for emitting laser beams; laser irradiation position changing parts 31, 33 for moving the laser irradiation part 35 relative to the width direction and conveyance direction of the sheet material; a machining pattern registration part for registering where to project the laser beams; and a control unit for emitting the laser beams while changing the position of irradiation positions on the basis of a registered machining pattern. The apparatus and method are further provided with a reference mark observation part and a reference mark interval measuring part 5, the control unit emitting the laser beams while successively correcting and changing the relative positions of movement of the laser irradiation position changing parts 31, 33 on the basis of the positions of the reference marks and the dimensions between the marks, and registered prescribed pattern information.