Recent intensive development tests of components for liquid-metal fast breeder reactors by use of sodium test loops require a reliable and easy method to solve problems associated with cold traps plugged by a large amount of impurities. Although the functioning of the cold traps is fundamental for controlling of sodium purity in such loops, problems sometimes occur because of plugging with sodium impurities. To establish a method to remove trapped impurities in the cold trap and thus to recover its trapping capacity, a regeneration test was made. Trapped impurities in the mesh region of the cold trap were heated with sodium up to 450 to 600°C, then drained into a small tank. The regenerations were made by this method more than 14 times. Chemical analysis of drained sodium in the tank indicated that all of the regenerations made were effective, and drained impurities were collected and concentrated successfully into the tank.