To provide a lock control method and a lock control system using a remote-controllable radio telephone set having excellent economical property and capable of performing unlocking time management of a lock easily and performing repair and change of a lock system easily.

A radio unlocking signal transmitted from a controller 4 through a circuit connection machine 3 is received by a radio telephone set 2, and the received signal is transmitted to a data transmitting and receiving part 6 in a control part of a lock 5 from a data transmitting and receiving part 7A of an adapter 7 connected with the radio telephone set 2 by radio communication to constitute a lock control method for unlocking the lock. Moreover, a lock control system 1 is constituted by the radio telephone set 2, the controller 4 transmitting a radio unlocking signal to the radio telephone set 2 through the circuit connection machine 3, and a data transmitting and receiving means transmitting and receiving data by radio communication between the data transmitting and receiving part 7A of the adapter 7 connected with the radio telephone set 2 and the data transmitting and receiving part 6 provided on a lock 5 side.