A cover includes a cover body, a guide, and an urging member. The cover body opens and closes an opening, formed in an accommodation housing. The guide is disposed in the accommodation housing, and extends in a direction crossing a direction, in which the cover body opens and closes the opening, partially at least. The urging member has a fastened end, fastened to the cover body, and an engagement end, engaged with the guide, and is expandable and contractable for accumulating an urging force as the cover body opens and closes the opening. The urging force urges the cover body in at least one of occasions, when the cover body opens the opening and when the cover body closes the opening.