This compressor system is provided with: a driving machine having a rotary-driven first output shaft and a second shaft that is rotary driven so as to reach the same speed as the first output shaft; a working-fluid-compressing first compressor to which the rotation of the first output shaft is transmitted; a working-fluid-compressing second compressor to which the rotation of the second output shaft is transmitted; a variable-speed step-up gear for increasing the speed of the first output shaft and transmitting the increased speed to the first compressor, said step-up gear being capable of varying the increased speed; and a constant-speed step-up gear for increasing the speed of the second output shaft and transmitting the increased speed to the second compressor, said step-up gear keeping the increased speed constant.