In this paper, detection of pedestrian groups and counting of the number of pedestrians in each group using “subtraction stereo” are discussed. Subtraction stereo is a stereo vision method that focuses on the movement of objects to make a stereo camera robust and produces range images for moving regions. Pedestrian groups are detected with a standard labeling, and three dimensional (3D) features of pedestrian groups are measured from range images obtained by subtraction stereo. Then a method to count the number of pedestrians in a group is proposed. The basic algorithm of the subtraction stereo is implemented on a commercially available stereo camera, and the effectiveness of the method to count the number of pedestrians is verified by experiments using the stereo camera.