Abstract: A Josephson quantum computing device and an integrated circuit using Josephson quantum computing devices which can realize a NOT gate operation controlled with 2 bits will be provided. The Josephson quantum computing device (1) comprises: a superconducting ring member (10) having a ?-junction (6) and a 0-junction (7); and a quantum state detecting member (20) constituted by a superconducting quantum interference device arranged outside of the superconducting ring member, wherein a bonding and an antibonding state brought about by a tunneling effect between a |?> and a |?> state as two states degenerate in energy of the superconducting ring member (10) are regarded as quantum bits. The bonding and antibonding states as the quantum bits are read out by the quantum state detecting member (20). The two bit controlled NOT gate operation can be performed by the two quantum bits comprising said quantum bits.