A quantum cryptography communication system for carrying out communication between a sending device, a receiving device and a generating device through a quantum communication channel transmitting a quantum and a classical communication channel transmitting data, the system comprising: a sending device controlling unit of the sending device, a receiving device controlling unit of the receiving device, and a generating device controlling unit of the generating device; a data sending unit of the sending device, a data receiving unit of the receiving device, and a generating device communicating unit of the generating device adapted to carry out communication through the classical communication channel, the data sending unit, the data receiving unit, and the generating device communicating unit being adapted to send/receive data according to instructions of the sending device controlling unit, the receiving device controlling unit, and the generating device controlling unit; an EPR, Einstein-Podolsky-Rosen, pair generating unit of the generating device adapted to generate entangled quantum state which is called an EPR pair according to an instruction of the generating device controlling unit, and to send it to a quantum communication channel, wherein the generating device controlling unit is adapted to issue said instruction to generate an EPR pair to the EPR pair generating unit based on setting information received from the sending device controlling unit by the generating device communicating unit; a sending device carrier receiving unit of the sending device adapted to receive a quantum carrier according to an instruction of the sending device controlling unit and to observe its quantum state, wherein the sending device controlling unit is adapted to receive an observation result from the sending device carrier receiving unit, to compute the observation result, and to send it to the classical communication channel through the data sending unit; a receiving device carrier receiving unit of the receiving device adapted to receive a quantum carrier according to the instruction of the receiving device controlling unit and to observe its quantum state; and the receiving device controlling unit is adapted to receive the observation result from the receiving device carrier receiving unit and to record the observation result in a memory unit, the memory unit being further adapted to record after received by the data receiving unit, the observation result of the sending device carrier receiving unit of the sending device, wherein the receiving device controlling unit is adapted to perform computation using the observation result recorded in the memory unit and the data received by the data receiving unit. a sending device controlling unit of the sending device, a receiving device controlling unit of the receiving device, and a generating device controlling unit of the generating device; a data sending unit of the sending device, a data receiving unit of the receiving device, and a generating device communicating unit of the generating device adapted to carry out communication through the classical communication channel, the data sending unit, the data receiving unit, and the generating device communicating unit being adapted to send/receive data according to instructions of the sending device controlling unit, the receiving device controlling unit, and the generating device controlling unit; an EPR, Einstein-Podolsky-Rosen, pair generating unit of the generating device adapted to generate entangled quantum state which is called an EPR pair according to an instruction of the generating device controlling unit, and to send it to a quantum communication channel, wherein the generating device controlling unit is adapted to issue said instruction to generate an EPR pair to the EPR pair generating unit based on setting information received from the sending device controlling unit by the generating device communicating unit; a sending device carrier receiving unit of the sending device adapted to receive a quantum carrier according to an instruction of the sending device controlling unit and to observe its quantum state, wherein the sending device controlling unit is adapted to receive an observation result from the sending device carrier receiving unit, to compute the observation result, and to send it to the classical communication channel through the data sending unit; a receiving device carrier receiving unit of the receiving device adapted to receive a quantum carrier according to the instruction of the receiving device controlling unit and to observe its quantum state; and the receiving device controlling unit is adapted to receive the observation result from the receiving device carrier receiving unit and to record the observation result in a memory unit, the memory unit being further adapted to record after received by the data receiving unit, the observation result of the sending device carrier receiving unit of the sending device, wherein the receiving device controlling unit is adapted to perform computation using the observation result recorded in the memory unit and the data received by the data receiving unit.