A position code consists of a plurality of cyclic main number sequences that are each shifted by a predetermined amount and arranged in a one-dimensional direction, each of the cyclic main number sequences consisting of cycles of a main number sequence that has a base number b and a length K and having K types of characteristic partial sequences with a predetermined length. A detection section is configured to detect, from each of at least two adjacent cyclic main number sequences among the plurality of cyclic main number sequences, a partial sequence having a length N and satisfying “K+K*(b−1)*N≦bN”. A determination section is configured to determine a place of each of the detected partial sequences having the length N in each of the cyclic main number sequences. An acquisition section is configured to acquire, based on the determined places, positional information given to a detected position in the position code.