Provided is a method for manufacturing a photoelectric-conversion-device capable of controlling the groove depth of a processed groove to a desired value. The method for manufacturing a photoelectric conversion device (10) includes a groove forming step of irradiating an intermediate-contact-layer separating groove (15) constituting a photoelectric conversion device (10) with a picosecond laser and of moving the picosecond laser relative to the intermediate-contact-layer separating groove (93), thereby forming a processed groove (15) in a predetermined scanning direction. In the groove forming step, interference fringes arranged in parallel in one direction are formed in an irradiated area corresponding to a beam diameter of the picosecond laser, and the picosecond laser is relatively moved such that the interference fringes are joined in the scanning direction.