Provided are an electromagnetic-induction-type position detector which can be small sized and in which interference errors do not occur, and a detection method. The present invention has: a stator having first and second main patterns and first and second sub-patterns; and a rotor having a main pattern part and a sub-pattern part, in which adjacent comb-shaped electrodes of the main pattern part and the sub-pattern part are connected to form a single loop; and when an excitation electric current is supplied to the first and second main patterns, an excitation voltage excited in the main pattern part is detected in the first and second sub-patterns via the sub-pattern part, and when an excitation electric current is supplied to the first and second sub-patterns, the excitation voltage excited in the sub-pattern part is detected in the first and second main patterns via the main pattern part.