An opening/closing door 10 for openably closing the opening of a housing includes: a door body; a locking member for holding the door body in a closed state by engagement with a part of the housing; and a lever 11 that is linked with the locking member and has one end rotatably supported by the door body, the door body including: a storage part 24 for storing the lever 11 along the surface of the door body when the locking member is placed in a locking state completely; and a protrusion 12 that protrudes outside the storage part 24 and comes into contact with the lever 11 when the locking member 13 is placed in the locking state incompletely.