Disclosed herein is a mobile robot which is capable of accurately calculating a position of the wireless signal source using a wireless signal, and allowing the mobile robot to accurately and rapidly return to a charging-stand using the calculated position. The position calculation system for a mobile robot includes: a wireless signal source for outputting a wireless signal continuously or periodically; and a mobile robot which includes a plurality of directional antennas for detecting the wireless signal outputted through the wireless signal source, wherein, the mobile robot calculates a direction of the wireless signal source via a rotation angle detected by the directional antennas, and calculates a distance separated from the wireless signal source using a wireless signal detection time difference between the directional antennas.