A mobile unit comprising: • called party number storing means for storing a called party number; • calling party number acquiring means for acquiring a calling party number corresponding to an incoming call; • ring counting means for counting the number of rings of the incoming call; • number checking means for checking a calling party number acquired by the calling party number acquiring means and a called party number stored in the called party number storing means; and • storage restricting means for storing a calling party number corresponding to the incoming call in a calling party number storing means when a calling party number acquired by the calling party number acquiring means corresponds to a called party number stored in the called party number storing means as a result of checking by the number checking means,for storing a calling party number corresponding to the incoming call in the calling party number storing means when a calling party number acquired by the calling party number acquiring means does not correspond to a called party number stored in the called party number storing means as a result of checking by the number checking means and the number of rings counted by the ring counting means is greater than a predetermined number, and for avoiding storing the calling party number corresponding to the incoming call in the calling party number storing means when a calling party number acquired by the calling party number acquiring means does not correspond to a called party number stored in the called party number storing means as a result of checking by the number checking means and the number of rings measured by the ring counting means is not more than the predetermined number. • called party number storing means for storing a called party number; • calling party number acquiring means for acquiring a calling party number corresponding to an incoming call; • ring counting means for counting the number of rings of the incoming call; • number checking means for checking a calling party number acquired by the calling party number acquiring means and a called party number stored in the called party number storing means; and • storage restricting means for storing a calling party number corresponding to the incoming call in a calling party number storing means when a calling party number acquired by the calling party number acquiring means corresponds to a called party number stored in the called party number storing means as a result of checking by the number checking means,for storing a calling party number corresponding to the incoming call in the calling party number storing means when a calling party number acquired by the calling party number acquiring means does not correspond to a called party number stored in the called party number storing means as a result of checking by the number checking means and the number of rings counted by the ring counting means is greater than a predetermined number, and for avoiding storing the calling party number corresponding to the incoming call in the calling party number storing means when a calling party number acquired by the calling party number acquiring means does not correspond to a called party number stored in the called party number storing means as a result of checking by the number checking means and the number of rings measured by the ring counting means is not more than the predetermined number.