A rotary machine is provided. The rotary machine includes a rotor disk including a plurality of slots, a plurality of blades mounted on an outer circumferential surface of the rotor disk, each of the blades having a root part inserted into an associated one of the slots, and a retainer restraining axial movement of the plurality of blades, wherein the retainer includes an inner fixing member inserted into a bottom of the slot, an outer fixing member inserted into a lower surface of the root part to abut against the inner fixing member, and a spacer inserted between the outer fixing member and the bottom of the slot to prevent the outer fixing member from being separated.