A superconducting magnet device of an embodiment includes a vacuum vessel, a superconducting coil, and an insulating load support. The insulating load support supports the superconducting coil through the thermal deformation cancellation 5 mechanism that generates a second deformation amount in a direction in which a first deformation amount applied from the superconducting coil to the insulating load support is canceled out due to thermal deformation occurring in the superconducting coil when the inside of the vacuum vessel is cooled to an extremely low temperature. The thermal deformation cancellation mechanism includes a thermal deformation member. The 10 thermal deformation member includes at least a material having a second coefficient of thermal expansion determined based on a first coefficient of thermal expansion of a material forming the superconducting coil, and generates the second deformation amount by thermally deforming in the same environment as the superconducting coil.