Working memory (WM) mechanisms for verbal, spatial, and object information have been extensively examined, yet those for kinetic information are less known. The current study explored the WM capacity and architecture of kinetic information by examining the maintenance of biological motion (BM) stimuli in WM. Human BM is the most salient and biologically significant kinetic information encountered in everyday life. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM. During a change detection task, we found that, at most, 3 to 4 BM stimuli could be retained in WM (Experiment 1). Next, we found that extra colors, spatial locations, or shapes remembered concurrently with BM stimuli (Experiments 2, 3, and 4, respectively), did not affect BM memory considerably. However, BM memory was affected by a concurrent memory task of non-BM movements (Experiment 5). These results support the hypothesis that an independent storage buffer of WM exists for kinetic information, which can hold up to 3 to 4 motion units.