To provide a protective cover capable of enhancing convenience in connecting and disconnecting an external output line and the like without impairing safety. In a protective cover placed on a side wall of a casing and covering a hollow part in which an output part of an apparatus housed in the casing is provided, the cover is characterized by including an outer lid which is supported by a hinge provided at an upper end to be openable and closable, and is provided, at a part close to a lower end, with a first locking member engaging with a catching member that is provided at a lower part of the hollow part, and an internal lid which is rotatably mounted to a position corresponding to the output part in an inner surface of the aforesaid outer lid to cover the output part. The internal lid is supported by a hinge.