A connection structure for a superconducting layer according to an embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer between the first superconducting layer and the second superconducting layer, the connection layer including crystal particles containing a rare earth element, barium, copper, and oxygen, the crystal particles having a major diameter distribution including a trimodal distribution. The trimodal distribution has first, second, and third distributions in which major diameter become small in this order. The aspect ratios of the crystal particles included in the first distribution and the second distribution include a bimodal distribution. The median value of the major diameters of the crystal particles included in the distribution on a higher aspect ratio side in the bimodal distribution is greater than the median value of the major diameters of the crystal particles included in the distribution on a lower aspect ratio side.