Provided is a protective bag for cards and the like in which four-corner outer edges of the protective bag run along circular arc-shaped four-corner outer edges of cards or the like and in which four-corner inner edges within the protective bag and circular arc-shaped four-corner outer edges of the cards or the like fit each other. The protective bag is a protective bag for cards and the like, the protective bag includes two rectangular-shaped films of equal shape and size which are superposed on each other without any positional shift, three sides of the rectangular shape are sealed so that an opening part is formed at one remaining side thereof. Each corner of the protective bag is formed into a circular-arc shape, and two base corner portions opposed to the opening part are opened without being sealed.