To provide a safe entry management system without taking much time in the case where a new user is added while additional construction can be carried out at a low cost.

An entry management device 2 provided to each of rooms receives a user ID vector and available room information from an IC card 1, and a disposable room ID vector is produced and is sent out. The IC card 1 calculates user joint ownership information from the room ID vector and user's own private information to send back. The entry management device 2 calculates room private information from a produced room noise vector, the random number table for each room and available room information, and it is combined with the user ID vector to calculate the room private information. Both joint ownership information is compared to decide whether entry is appropriate or not. The random number table stored in every entry management device 2 is not required for renewal in the case a new user is added. In the case of decision, the random number table and user private information can be kept in secret, and forgery and alternation of the IC card 1 can be prevented.