1. A positioning method comprising: (a) executing a cumulative addition for either one of the polarities on each of an I and Q components of a received positioning signal, which is spread-modulated with a spread code reversed in polarity by navigation data; (b) calculating sum of squares of the results of the cumulative addition in step (a); (c) calculating correlation between the sum of squares calculated in step (b) with a replica code of the spread code; and (d) executing a positioning calculation of the present position based on the result of the correlation calculation in step (c).