A method for forming a pattern according to an embodiment, includes forming above a first film film patterns of a second film; forming film patterns of the first film by etching the first film using the film patterns of the second film as a mask; converting the film patterns of the second film into film patterns whose width are narrower than the film patterns of the first film by performing a slimming process; forming film patterns of a third film on both sidewalls of the film patterns of the first film and the film patterns of the second film after the slimming process; and etching the first film using the film patterns of the third film as a mask after the film patterns of the second film being removed.