A tag reader communicating with a wireless tag, the tag reader comprising: a phase calculation section (S10 and S110) that sequentially calculates a phase (φ r) of a reception wave as an electric wave transmitted from the wireless tag and received by the tag reader in response to an electric wave transmitted to the wireless tag; characterized by a phase difference calculation section that calculates a phase difference (δφ) as a difference of phases calculated at two time points by the phase calculation section; and a tag angle calculation section that calculates a tag angle (θ) as an angle between a straight line connecting an antenna included in the tag reader and the wireless tag and a line on which the wireless tag is moving, in accordance with the phase difference and a tag travel distance as a travel distance of the wireless tag during the two time points, wherein: the phase difference calculation section calculates two values of the phase difference with at least one of the two time points for calculation of the phase difference being set to a different time point; the tag angle calculation section calculates a first tag angle and a second tag angle each as the tag angle in accordance with the two values of the phase difference; and the tag reader further comprises a tag distance calculation section that calculates an antenna-tag minimum distance (Lmin) as a minimum distance from the line on which the wireless tag is moving to the antenna in accordance with a distance between a position at the tag angle having the first tag angle and a position at the tag angle having the second tag angle, the first tag angle, and the second tag angle. a phase calculation section (S10 and S110) that sequentially calculates a phase (φ r) of a reception wave as an electric wave transmitted from the wireless tag and received by the tag reader in response to an electric wave transmitted to the wireless tag; characterized by a phase difference calculation section that calculates a phase difference (δφ) as a difference of phases calculated at two time points by the phase calculation section; and a tag angle calculation section that calculates a tag angle (θ) as an angle between a straight line connecting an antenna included in the tag reader and the wireless tag and a line on which the wireless tag is moving, in accordance with the phase difference and a tag travel distance as a travel distance of the wireless tag during the two time points, wherein: the phase difference calculation section calculates two values of the phase difference with at least one of the two time points for calculation of the phase difference being set to a different time point; the tag angle calculation section calculates a first tag angle and a second tag angle each as the tag angle in accordance with the two values of the phase difference; and the tag reader further comprises a tag distance calculation section that calculates an antenna-tag minimum distance (Lmin) as a minimum distance from the line on which the wireless tag is moving to the antenna in accordance with a distance between a position at the tag angle having the first tag angle and a position at the tag angle having the second tag angle, the first tag angle, and the second tag angle. the phase difference calculation section calculates two values of the phase difference with at least one of the two time points for calculation of the phase difference being set to a different time point; the tag angle calculation section calculates a first tag angle and a second tag angle each as the tag angle in accordance with the two values of the phase difference; and the tag reader further comprises a tag distance calculation section that calculates an antenna-tag minimum distance (Lmin) as a minimum distance from the line on which the wireless tag is moving to the antenna in accordance with a distance between a position at the tag angle having the first tag angle and a position at the tag angle having the second tag angle, the first tag angle, and the second tag angle.