A quantum gate device (10, 20), comprising: a) a first superconducting circuit configured to resonate at a first resonance frequency, the first superconducting circuit including: a-1) a first Josephson device which is a single Josephson device; a-2) a second Josephson device group in which n Josephson devices (1121, 1122) are connected in series by a line made of a superconductor, where n is an integer equal to or greater than two and each of the n Josephson devices has a Josephson energy greater than n times a Josephson energy of the first Josephson device; a-3) a first capacitor; and a-4) a first line made of a superconductor and configured to form a partial superconducting circuit by connecting the first Josephson device and the second Josephson device group in a ring-like form, as well as to connect the partial superconducting circuit and the first capacitor in parallel; b) a second superconducting circuit (12, 12A, 12B, 12C) configured to resonate at a second resonance frequency, including at least one Josephson device (121, 121A, 121B, 121C), a second capacitor, and a second line (125,125A,125B,125C) made of a superconductor; c) a connector configured to connect the first superconducting circuit and the second superconducting circuit, including a connector capacitor as well as a third line made of a superconductor and connected to each of two poles of the connector capacitor; d) a magnetic field applier configured to apply a static magnetic field to the partial superconducting circuit; and e) an electromagnetic wave irradiator configured to irradiate the first superconducting circuit with an electromagnetic wave having a difference frequency which is equal to a difference between the first resonance frequency and the second resonance frequency. a) a first superconducting circuit configured to resonate at a first resonance frequency, the first superconducting circuit including: a-1) a first Josephson device which is a single Josephson device; a-2) a second Josephson device group in which n Josephson devices (1121, 1122) are connected in series by a line made of a superconductor, where n is an integer equal to or greater than two and each of the n Josephson devices has a Josephson energy greater than n times a Josephson energy of the first Josephson device; a-3) a first capacitor; and a-4) a first line made of a superconductor and configured to form a partial superconducting circuit by connecting the first Josephson device and the second Josephson device group in a ring-like form, as well as to connect the partial superconducting circuit and the first capacitor in parallel; a-1) a first Josephson device which is a single Josephson device; a-2) a second Josephson device group in which n Josephson devices (1121, 1122) are connected in series by a line made of a superconductor, where n is an integer equal to or greater than two and each of the n Josephson devices has a Josephson energy greater than n times a Josephson energy of the first Josephson device; a-3) a first capacitor; and a-4) a first line made of a superconductor and configured to form a partial superconducting circuit by connecting the first Josephson device and the second Josephson device group in a ring-like form, as well as to connect the partial superconducting circuit and the first capacitor in parallel; b) a second superconducting circuit (12, 12A, 12B, 12C) configured to resonate at a second resonance frequency, including at least one Josephson device (121, 121A, 121B, 121C), a second capacitor, and a second line (125,125A,125B,125C) made of a superconductor; c) a connector configured to connect the first superconducting circuit and the second superconducting circuit, including a connector capacitor as well as a third line made of a superconductor and connected to each of two poles of the connector capacitor; d) a magnetic field applier configured to apply a static magnetic field to the partial superconducting circuit; and e) an electromagnetic wave irradiator configured to irradiate the first superconducting circuit with an electromagnetic wave having a difference frequency which is equal to a difference between the first resonance frequency and the second resonance frequency.