A position detector, includes: a scale having pattern arrays formed in different cycles in a movement direction an obtaining unit which obtains signals in accordance with the pattern arrays; a first deriving unit which derives a temporal position of the scale relative to the obtaining unit based on the signals; a second deriving unit which derives a displacement amount of the scale relative to the obtaining unit based on one or more signals of the signals; and a determinates which determines a determined position of the scale relative to the obtaining unit based on the temporal position and the displacement amount, wherein the determinator determines the determined position based on a result of comparison between a difference between first and second temporal positions respectively calculated by the first and second deriving units at first and second positions and a displacement amount from the first position to the second position.