When using a supernumerary limb, it is necessary to pay appropriate attention to the supernumerary limb and recognize its state. In this study, we verified whether the posture of a supernumerary limb removed from a human and placed in an environment could be perceived from the tactile feedback in a dual-task. Then, we examined the effect of perceivability on dual-task performance. In the former verification, participants were asked to answer the position of a randomly stopped supernumerary limb while pouring a prescribed volume of water with their natural bodies. The latter was examined with 2 kinds of dual-tasks. Dual-task A required the tasks on the natural body and the supernumerary limb sides to have a common perceptual modality. Dual-task B did not require the tasks on the natural body and supernumerary limb sides to have a common perceptual modality. Thus, supernumerary limb location identification accuracy was as good in dual-task conditions as in single-task conditions. In addition, task performance in dual-task B was improved by the presence of tactile feedback.