In a pattern forming method, a first L & S pattern is formed on a wafer; a first protective layer, a second L & S pattern having a perpendicular periodic direction to that of the first L & S pattern, and a photoresist layer are formed to cover the first L & S pattern; a third pattern having first apertures is formed in the photoresist layer to be overlapped with a part of the second L & S pattern; second apertures are formed in the first protective layer via the first apertures; and a part of the first L & S pattern is removed via the second apertures. Accordingly, a pattern including a non-periodic portion finer than a resolution limit of an exposure apparatus is formed.