The method of managing time M, at which maintenance of a gas compressor multiple system incorporating therein a plurality of gas compressors should be carried out, involves making a comparison between a value of M and a predetermined time N for necessary maintenance to carry out the maintenance when the value of M is larger than or substantially equal to a value of N, where M is equal to the product of the operating time T of the system, the average load factor L, and a safety factor C.