A bearing includes: an outside portion; an inside portion which is rotatably assembled to the outside portion; a rotating body arranged in a space formed when the outside portion and the inside portion are assembled; a first sealing portion which is integrally molded with the outside portion and seals the space by abutting against the inside portion through elastic deformation caused when assembled; and a second sealing portion which is integrally molded with the inside portion and seals the space by abutting against the outside portion through elastic deformation caused when assembled.