The invention provides a production process of a gas turbine capable of being applied to various cycles. A principal part of a gas turbine is set in advance based on roughly set conditions, and the number of stages of a compressor and the number of stages of a turbine, which can provide conditions suitable for a desired cycle, are set based on the set principal part. The compressor and the turbine each having the set number of stages and included in the principal part are combined with each other to construct the gas turbine. When the set number of stages of the compressor or the turbine differs among a plurality of desired cycles, a substantially disk-shaped member having an outer periphery, which forms an inner peripheral wall of a substantially annular flow passage of the compressor or the turbine, is assembled into the cycle having a smaller number of stages so that the bearing-to-bearing distance is kept constant in the gas turbine operated in the plurality of desired cycles.