A method for installing a compressor includes a preparing step of preparing a base plate that supports a support leg onto a foundation, a level adjusting member disposing step of disposing a plurality of level adjusting members having a wedge shape onto the base plate along an outline of a lower end portion of the support leg, an adjusting step of adjusting a horizontal level of a rotary machine main body by adjusting pushing amounts of the level adjusting members to the lower end portion of the support leg, and a fixing step of fixing positions of the support leg and the level adjusting members with respect to the base plate by welding the support leg to the plurality of level adjusting members.