A quantum bit device according to the present invention includes a first quantum bit substrate 10 which includes a first superconductive wiring 13 disposed to have a magnetically coupled portion with a first superconductive magnetic flux quantum bit 14 on a surface thereof, a second quantum bit substrate 11 which includes a second superconductive wiring 13 disposed to have a magnetically coupled portion with a second superconductive magnetic flux quantum bit 14 on a surface thereof, and a base substrate 12 which includes a third superconductive wiring 13 configured by two superconductive wirings extending parallel to each other on a surface thereof. The first and second quantum bit substrates are placed on the base substrate, two end portions of the first superconductive wiring and two end portions on one side of the third superconductive wiring are joined via superconductive solders 15, two end portions of the second superconductive wiring and two end portions on the other side of the third superconductive wiring are joined via superconductive solders 15, and three of the first to third superconductive wirings form one continuous superconductive loop.