Disclosed are a bidirectional information sharing system and a method using a wireless data network that can improve convenience of use by setting notification information regarding specific days which is set to replace sharing information of an unspecified third party that places a call and output the sharing information to output the notification information regarding specified days on the screen when receiving a call of the unspecified third party and input the feelings or inquiries of a user using the mobile phone sharing information of the user to allow the called party to previously know the corresponding contents before a telephone conversation at the time of call connection, and change and set sharing information so as to officially inform only close acquaintances of a relationship status of lovers or the like rather than informing unspecified individuals, in particular, inform or introduce acquaintances of the called party of relationship status.