An imaging device for receiving a radio signal output from an RF tag attached to a subject to acquire identification information of the subject, includes: an imaging unit for continuously imaging a plurality of subjects to acquire a moving image; a radio receiver for receiving a plurality of radio signals respectively output from RF tags attached to the subjects to acquire a plurality of units of subject identification information respectively indicated by the radio signals, the subject identification information identifying a corresponding subject, the radio receiver moving together with the imaging unit and having directivity in a direction approximately the same as an imaging direction of the imaging unit; a moving amount calculation unit for calculating a moving amount of the radio receiver based on the acquired moving image; and a subject direction specifying unit for specifying directions of the subjects respectively identified by the plurality of units of subject identification information based on changes in field intensities of the radio signals, the changes corresponding to the moving amount of the radio receiver.