A pattern forming method includes forming a first film patterned in a line and space shape on an underlayer film, the line and space shape including lines and a space arranged therebetween, forming a second film to cover the first film, removing the second film to form the second film on a side surface of the first film in a line shape, forming a third film to cover the first film and the second film, removing the third film formed on the first film and the second film to form the third film on a side surface of the second film, and converting the third film after removing the third film formed on the first film and the second film, wherein the third film is comprised of an organic metal compound, the organic metal compound having characteristic to increase etching tolerance when the organic metal compound undergoes a predetermined process.