A microwave-identification method that allows mobile phones to be utilized for indoor localization is proposed. Since the conventional localization method cannot identify specific microwaves because their identification code is encrypted, a system that utilizes web-access time as a measure of identification is proposed. In this system, a microwave is received at an access point (AP) at a certain web-access time, and it is identified as a microwave accessing the web. The proposed system estimates the position of a person as near the AP that received the web-access microwave (WAM). To achieve high identification accuracy, the proposed system consists of a spurious-microwave filter, a WAM-candidate-detection block, and a reliability-calculation block. The proposed system applying the proposed microwave-identification method was validated experimentally and by simulation. According to the simulation, the proposed system using 100 APs in a large-scale indoor localization environment achieved 95% identification accuracy.