A method of cycling a nuclear fuel for a fast breeder and a minor actinoids annihilation reactor, which provides a nuclear fuel cycle having technical advantages, such as a safety inherent in a nuclear reactor, a short fuel doubling time and a high uranium resources utilization factor, and economical advantages, comprising the steps of: preparing sphere pack type fuel pins including a nuclear fuel containing uranium-plutonium-mixed nitride fuel and a minor actinoids nitride fuel, and a sodium heat bonding material, installing the fuel pins in a reactor core and burning the same, subjecting the used fuel to fused salt electrolysis, converting the uranium, plutonium and minor actinoids deposited on a cathode into a high-order nitride, recovering the high-order nitride, converting the recovered high-order nitride into mononitride, and manufacturing a nuclear fuel, which contains a uranium-plutonium-mixed nitride fuel and a minor actinoids nitride fuel, from the mononitride.