To provide a method and apparatus for halving by laser which can reduce a problem of staining of a focus lens and a workpiece caused by generated transpired gas, in halving a resin film by laser.

When a film with a resin layer formed on an electromagnetic wave shield layer is irradiated with a laser beam converged by a lens, and a part of the film in the thickness direction is removed, the periphery of an optical path of the laser beam passed through the lens is covered with a casing that has an irradiation port of the laser beam, and the irradiation port is separated from the film at least by 10 mm, and while air is supplied into the casing, the transpired gas is exhausted outside the casing, so that a pressure inside the casing is set to +0.02 MPa to +0.05 MPa relative to the pressure of the atmosphere in which the film is disposed.