A measurement apparatus (2) outputs from a first antenna pair (3) transmission signals (St 11 ) and (St 12 ) whose phase difference (”Æ 1 ) changes over time. A target object (21) simultaneously receives the transmission signals (St 11 ) and (St 12 ) from a target-side antenna (22) and returns to the measurement apparatus (2) information (DÆ) according to the positional relationship between the target object (21) and the measurement apparatus (2) determined from a reception signal (Sr 1 ). The measurement apparatus (2) outputs from a second antenna pair (4) transmission signals (St 21 ) and (St 22 ) whose phase difference (”Æ 2 ) changes over time. The target object (21) simultaneously receives the transmission signals (St 21 ) and (St 22 ) from the target-side antenna (22) and returns to the measurement apparatus (2) the information (DÆ) corresponding to the positional relationship between the target object (21) and the measurement apparatus (2) determined from a reception signal (Sr 2 ). The measurement apparatus (2) identifies a direction (¸) of the target object (21) on the basis of these two pieces of information (DÆ).
