The present invention relates to a cover that is used as a backrest cover in daily use and also as a life jacket in an emergency. More particularly, the present invention relates to a backrest cover including: a front portion configured to cover a front surface of the backrest; a rear portion configured to cover a rear surface of the backrest; a connector configured to extend across an upper end of the backrest, connecting the front and back portions; and a buoyancy body provided in at least one of the front portion, the rear portion, and the connector.