This paper presents a multipath detection method using asynchronous multiple GNSS receivers. Our proposed method is based on the consistency analysis between inter-antenna phase difference and antenna attitude. The multipath detection accuracy is expected to be improved because the fluctuation of the phase difference caused by the multipath signals is directly observed in this method. Moreover, this method is applicable to asynchronous receivers by using receiver clock error and Doppler frequency shift. Experimental results under multipath environments are presented to show that the proposed method is valid.