A cryostat includes a room temperature vessel, a low temperature vessel, and a refrigeration mechanism. The room temperature vessel includes a room temperature tank, an outer neck tube and a sealing head. The low temperature vessel includes a low temperature tank, an inner neck tube and a liquefaction chamber. The liquefaction chamber corresponds to the first opening and passes through the first opening. The refrigeration mechanism includes a device panel and a refrigeration device. The device panel is disposed on the sealing head. The refrigeration device includes a body and a cold finger. The body is disposed at the device panel. The cold finger is connected with the body and extends into the liquefaction chamber.