A noise reducing device for an apparatus provided with a plurality of discharge passages and that is to be used for reducing noise originating from discharge gas discharged from the discharge passages. The noise reducing device including: (a) a plurality of primary sound reducers that are connected to the plurality of discharge passages of the apparatus; and (b) a secondary sound reducer that accommodates a part of each of the plurality of primary sound reducers including at least a discharge port and that includes a space that allows the discharge gas that has passed through the primary sound reducers and been discharged from the discharge ports to pass therethrough, and a system-to-outside discharge unit that allows the discharge gas that has passed through the space to be discharged to outside of the system.