Provided is a method for measuring a neighbor cell signal in a portable terminal includes acquiring a minimum required quality level value and a threshold for an intra-frequency measurement from received system information; calculating a measured cell quality value after the acquiring step; and commencing a neighbor cell signal measurement for an intra-frequency cell reselection when a value acquired by subtracting the minimum required quality level value from the measured cell quality value is less than or equal to a value acquired by adding the threshold and a certain signal strength value over a certain time. In the neighbor cell signal measurement for the cell reselection, the unnecessary neighbor cell signal measurement can be avoided to reduce the power consumption and extend the battery lifetime.