PROBLEM TO BE SOLVED : To provide a property guide system enabling a user to receive key data for performing the locking or unlocking of a property through a mobile communication line.SOLUTION : An office server 40 owned by a real estate agent 40 has a database for storing data of properties to be mediated and an electronic key data storage part for storing electronic key data for locking and unlocking the electronic lock of the entrance of each property according to a prescribed condition in association with each property. The user connects a portable terminal 10 to the office server 40 through the mobile communication line to receive the data of a desired property and the corresponding electronic key data, and writes the electronic key data in an IC card 20.