Provided is a semiconductor device that can be reduced in size while variation in shape among circuit patterns is reduced. The semiconductor device includes multiple circuit patterns and first dummy patterns. The multiple circuit patterns are disposed at regular intervals, and are used as part of the circuit. The multiple circuit patterns consist of two outermost circuit patterns and the other inner circuit patterns. The first dummy patterns are disposed on outer sides of the two outermost circuit patterns, respectively. The distance between each of the outermost circuit patterns and the corresponding first dummy pattern is equal to a distance between any adjacent two of the circuit patterns. A width of each of the first dummy patterns is smaller than a width of any of the circuit patterns, and is equal to a minimum design rule width, for example.