A capacity varying device for a scroll compressor is provided. The device may include a fixed scroll and an orbiting scroll both located in a casing, a low pressure passage formed by an orbiting motion of the orbiting scroll that communicates with a suction side, an intermediate pressure passage formed by the orbiting motion of the orbiting scroll that communicates with an intermediate pressure side, a rotating device rotatably coupled to the fixed scroll and having a connection passage therein, and an operating device mounted at the fixed scroll and configured to rotate the rotating device such that the low pressure passage and the intermediate pressure passage are connected/disconnected to/from each other via the connection passage of the rotating device. Accordingly, a capacity for compressing gas may be varied, a size of the device may be reduced due to a compact configuration and structure for varying the capacity, and also a fast response to the varying of the capacity may be provided.