A communication apparatus includes an antenna, a detecting section, and a determining section. The antenna receives a radio wave transmitted from a wireless tag. The detecting section detects a phase of the radio wave. The determining section determines that the wireless tag is present outside a predetermined range if a phase difference between a phase measured if a relative position of the antenna with respect to the wireless tag is a first position within a first range and a phase measured if the relative position is a second position within the first range is smaller than a threshold or if a phase difference between a phase measured if the relative position is a third position within a second range different from the first range and a phase measured if the relative position is a fourth position within the second range is smaller than the threshold.