Provided is a superconducting accelerating cavity 30 including: a cavity main body 10 formed of a superconducting material into a cylindrical shape; and a refrigerant tank 20 installed around the cavity main body 10 and storing a refrigerant which is supplied from the outside through a supply port 20a into a space formed between the refrigerant tank and the outer circumferential surface of the cavity main body 10, wherein the outer circumferential surface of the cavity main body 10 is coated with a metal coating layer 10a having a higher conductivity than the superconducting material.