1. A group analysis system comprising a plurality of sensor terminals and a controller connected to said plural sensor terminals, wherein each of said sensor terminals has a first sensor to detect relative positions and a second sensor to acquire surrounding environmental information, and wherein said controller has an input-output unit to acquire sensor signals from said first and second sensors in each of said sensor terminals, and an analyzer to set an initial group of said sensor terminals with said sensor signals from said first sensor, extract the feature quantity of said initial group from said sensor signals of said second sensor received from each of said sensor terminals constituting said initial group, and decide a group to which a sensor terminal not belonging to said initial group belongs by comparing said feature quantity of said initial group with the feature quantity, corresponding to said feature quantity of said initial group, extracted from sensor signals of said second sensor of said sensor terminal not belonging to said initial group.