A cryostat comprising: a room temperature vessel comprising a room temperature tank, an outer neck tube and a sealing head, the outer neck tube communicating with the room temperature tank, a first opening being disposed at the room temperature tank, the sealing head being disposed to cover the room temperature tank, a second opening and a third opening being disposed at the sealing head, the first opening corresponding to the third opening, the outer neck tube corresponding to the second opening and being exposed outside the sealing head through the second opening, and an outer circumference of the outer neck tube being in sealingly contact with the second opening of the sealing head; a low temperature vessel comprising a low temperature tank, an inner neck tube and a liquefaction chamber, the inner neck tube being independent of the liquefaction chamber and communicating with the low temperature tank, the low temperature vessel being housed inside the room temperature tank, part of the inner neck tube being located inside the outer neck tube, part of the liquefaction chamber being located inside the room temperature tank, and the liquefaction chamber corresponding to the first opening and passing through the first opening; and a refrigeration mechanism comprising a device panel and a refrigeration device, the device panel being disposed at the sealing head and having through holes respectively corresponding to the second opening and the third opening, the refrigeration device being installed to the device panel, the refrigeration device comprising a body and a cold finger, the body being disposed at the device panel, and the cold finger being connected with the body and extending into the liquefaction chamber, wherein the sealing head is a flat plate that is fixedly connected with the room temperature tank and the device panel is detachably connected with the sealing head. a room temperature vessel comprising a room temperature tank, an outer neck tube and a sealing head, the outer neck tube communicating with the room temperature tank, a first opening being disposed at the room temperature tank, the sealing head being disposed to cover the room temperature tank, a second opening and a third opening being disposed at the sealing head, the first opening corresponding to the third opening, the outer neck tube corresponding to the second opening and being exposed outside the sealing head through the second opening, and an outer circumference of the outer neck tube being in sealingly contact with the second opening of the sealing head; a low temperature vessel comprising a low temperature tank, an inner neck tube and a liquefaction chamber, the inner neck tube being independent of the liquefaction chamber and communicating with the low temperature tank, the low temperature vessel being housed inside the room temperature tank, part of the inner neck tube being located inside the outer neck tube, part of the liquefaction chamber being located inside the room temperature tank, and the liquefaction chamber corresponding to the first opening and passing through the first opening; and a refrigeration mechanism comprising a device panel and a refrigeration device, the device panel being disposed at the sealing head and having through holes respectively corresponding to the second opening and the third opening, the refrigeration device being installed to the device panel, the refrigeration device comprising a body and a cold finger, the body being disposed at the device panel, and the cold finger being connected with the body and extending into the liquefaction chamber, wherein the sealing head is a flat plate that is fixedly connected with the room temperature tank and the device panel is detachably connected with the sealing head.