The present invention provides a method for manufacturing a liquid crystal display device, which hardly causes alignment defects in the case of forming a horizontal alignment film by employing a photo-alignment treatment. The method for manufacturing a liquid crystal display device of the present invention includes a step of forming a horizontal alignment film by carrying out a photo-alignment treatment of irradiating a photo-alignment film material applied to at least one substrate of a pair of substrates with light, wherein the photo-alignment treatment is a treatment for irradiating the same region with light two or more times from a slanting direction with respect to a surface of the at least one substrate of the pair of substrates, and at least two of lights applied two or more times in the photo-alignment treatment are polarized lights applied from directions mutually different at 90° or greater.