A connection structure of a superconducting layer according to an embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer provided between the first superconducting layer and the second superconducting layer and including a first substance containing a rare earth element, barium, copper, and oxygen and a second substance containing a metal element, in which a first region per unit area at a first interface between the first superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the first superconducting layer are in contact with each other, and a second region per unit area at a second interface between the second superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the second superconducting layer are in contact with each other.