In this paper, an omnidirectional source tracking method based on sensitivity difference of microphone pairs is proposed. In the conventional method, we developed the direction estimation method based on a histogram integrating the estimation results of multiple two-microphone pairs. However, the estimation accuracy degradation often occurs despite the number of microphones. When a sound source exists at a wide angle to the microphone pairs, the estimation direction indicates highly sensitive to the measurement error of TDOA(Time-Difference-Of-Arrival) between microphones, and the estimation accuracy is greatly degradated. Therefore, it is considered that the same reliability should not be given to all estimation results to the same sound source. Because the estimation accuracy differs for each microphone pairs even for the same sound source, In the proposed method, such a difficulty is resolved by selecting the microphone pair used for the estimation, then the another pair is used just to judge whether the source exists in front or in back. As a result, the estimation accuracy can be improved with half the number of microphones of the conventional method. The effectiveness of method is shown from several experimental results.