In a system carrying out cryptography communication using a quantum, it is aimed to correctly verify a quantum state received at the commit phase according to the quantum bit string commitment system, even if not maintaining the quantum state until the open phase but immediately observing the quantum state. According to the present invention, the quantum cryptography communication system includes a sending device 1 and a receiving device 2 connected by a quantum communication channel 11 and a classical communication channel 12. A carrier sending unit 14 of the sending device 1 sends a quantum to the quantum communication channel 11, a carrier receiving unit 17 of the receiving device 2 receives the quantum and observes its quantum state. A receiving device controlling unit 16 computes using the observation result and data sent from a data sending unit 15 of the sending device 1 to a data receiving unit 18 of the receiving device 2 through the classical communication channel 12, and outputs the result of cryptography communication derived from the computation.