A novel positioning method based on the difference between phases of carrier waves transmitted from closely located pseudolite antennas is proposed. This method can avoid the major problems with the conventional positioning method using pseudolites. A three-channel pseudolite applying the proposed method was developed, and its positioning performance was experimentally evaluated. In the experiment, carrier-phase differences were measured at thirty-three points in a field of 4 × 4 m; their two-dimensional positions were estimated. The experimental measurements show that the method can achieve decimeter- to meter-level positioning accuracy. They also show that many factors, such as dilution of precision, carrier-to-noise density ratio, multipath propagation, and phase-center variation of antennas, affect the positioning performance.