Heat regenerating material, regenerator, refrigerator, superconducting magnet, nuclear magnetic resonance imaging apparatus, nuclear magnetic resonance apparatus, cryopump, and magnetic field application type single crystal pulling apparatus

A regenerator comprising:

• a plurality of heat regenerating materials, which comprise
• a plurality of heat regenerating substance particles having a maximum volume specific heat value of 0.3 J/cm3·K or more at a temperature of 20 K or lower;
• and
• a binder bonding the heat regenerating substance particles, the binder containing water insoluble resin, wherein
• the water insoluble resin is a polyvinyl butyral resin,
• the heat regenerating material has a particle diameter of 500 μm or less, and the binder has an occupancy ratio of more than 5% by volume in the heat regenerating material.