<p>A plug-in unit electrically connected to a sub rack enabling the detachable fitting of a module thereto while shielding the plug-in unit from electromagnetic wave and a communication device. The plug-in unit comprises a second shield cover member (70) covering the interface part (60), coming into contact with the peripheral surface of the interface part (60), and having a first opening part (71) exposing the connection part (61) thereof to the outside at the front end of the interface part (60) and a shield mechanism (S) interposed between the second shield cover member (70) and a front cover member (50) and covering a clearance between the second opening part (51) of the front cover member (50) and the outer peripheral surface of the second shield cover member (70).</p>
