The purpose is manufacturing a photoelectric conversion device with excellent photoelectric conversion characteristics typified by a solar cell with effective use of a silicon material. A single crystal silicon layer is irradiated with a laser beam through an optical modulator to form an uneven structure on a surface thereof. The single crystal silicon layer is obtained in the following manner; an embrittlement layer is formed in a single crystal silicon substrate; one surface of a supporting substrate and one surface of an insulating layer formed over the single crystal silicon substrate are disposed to be in contact and bonded; heat treatment is performed; and the single crystal silicon layer is formed over the supporting substrate by separating part of the single crystal silicon substrate fixed to the supporting substrate along the embrittlement layer or a periphery of the embrittlement layer. Then, irradiation with a laser beam is performed on a separation surface of the single crystal silicon layer through an optical modulator which modulates light intensity regularly, and unevenness is formed on the surface. Due to the unevenness, reflection of incident light is reduced and absorptance with respect to light is improved, therefore, photoelectric conversion efficiency of the photoelectric conversion device is improved.