1. A positioning method executed on an electric device, comprising: executing a first correlation accumulation process adapted to execute a correlation accumulation on a received signal, a positioning signal spread-modulated with a spread code, and a replica code of the spread code while shifting a phase of the replica code in a first phase search range; setting a second phase search range narrower than the first phase search range based on an accumulated correlation value at a first timing in the first correlation accumulation process; executing a second correlation accumulation process adapted to execute a correlation accumulation on the received signal and the replica code while shifting the phase of the replica code in the second phase search range; determining appropriateness of the second phase search range set in the setting step, based on the accumulated correlation value at the first timing and an accumulated correlation value at a second timing that is subsequent to the first timing in the first correlation accumulation process; and positioning by executing a predetermined positioning calculation using a processing result of the second correlation accumulation process, if the second phase search range is determined appropriate; positioning by executing the predetermined positioning calculation based on an accumulated correlation value in the first correlation accumulation process after the first timing, until the second phase search range is determined appropriate in the determining step; and newly setting the second phase search range based on an accumulated correlation value in the first correlation accumulation process, if the second phase search range is determined inappropriate in the determining step, the first correlation accumulation process being a process of executing the correlation accumulation while shifting the phase of the replica code by a first unit phase interval, the second correlation accumulation process being a process of executing the correlation accumulation while shifting the phase of the replica code by a second unit phase interval narrower than the first unit phase interval, the determining appropriateness of the second phase search range being based on whether or not a phase with a maximum accumulated correlation value at the first timing and a phase with a maximum accumulated correlation value at the second timing in the first correlation accumulation process satisfy a predetermined approximation condition.