Single-phase antiperovskite nitride GeNCo3 with space group PM (3) over barM is successfully synthesized by a solid-gas reaction. The crystal structure, magnetism, specific heat at low temperatures, Hall effect, and electrical and thermal transport properties are widely investigated. Exhilaratingly, a canonical spin-glass (SG) behavior is observed in GeNCo3 with a freezing temperature T-0 = 79.43 K, dynamical exponent z nu = 6.156, and flipping time tau(0) = 5.0 X 10(-12) s. The origin of the SG state in GeNCo3 is likely due to the atomic disorder introduced by the Ge vacancies. This is further proven by the measurements of Ge0.9NCo3 with more Ge deficiencies.