To efficiently cool a superconductive coil housed in a ring-like cooling vessel from the inner peripheral side also.

This cooling vessel wherein a superconductive coil formed by winding a superconductive wire is housed, and the superconductive coil is cooled to a superconductive temperature by an introduced cooling medium, is provided with an outer wall constituted of: a cylindrical inner peripheral wall arranged on the inner peripheral side of the superconductive coil; a cylindrical outer peripheral wall arranged on the outer peripheral side of the superconductive coil; and both annular end sidewalls continuing to both axial edges of the inner peripheral wall and the outer peripheral wall and arranged on both axial end surface sides of the superconductive coil. The outer wall is formed of a material having low thermal conductivity, and a thermally-conducting member formed of a material having thermal conductivity higher than those of the inner peripheral wall, the outer peripheral wall and both the end sidewalls is interposed between the inner peripheral wall and the superconductive coil.