Disclosed is a plate-making method and a computer-to-cylinder type lithographic printing method, each of which comprises filtering an oil-based ink; forming an image directly on a plate material by an ink jet process comprising ejecting said filtered oil-based ink using electrostatic field based on signals of image data; and fixing said formed image to prepare a printing plate. Also disclosed are a plate-making apparatus and a computer-to-cylinder type lithographic printing method suitable for these methods, respectively.