Provided is a method of manufacturing a rotary machine, which includes: a casing forming process of forming a casing of the rotary machine that has multiple opening parts and suctions and discharges a fluid; a surface activating process of supplying a pretreatment liquid into the casing, then discharging the pretreatment liquid from the casing through the opening parts, and activating an inner surface of the casing after the casing forming process; a plating process of performing supply and discharge of a plating liquid into and from the easing through the opening parts to circulate the plating liquid and plating the inner surface of the casing after the surface activating process; and an assembling process of providing a rotating body that is rotatable relative to the casing so as to he covered from an outer circumference side by the casing plated in the plating process.