To provide a marine safety ladder that makes rescue possible within a short time, without posing any risk of contact with a pleasure boat or the like, without causing any additional concern in the operation of boats during docking and departure, without the risk of injury to a person who has fallen, etc., and without the risk of falling when the ladder is being stowed.A top hinge member (67) is connected and fixed to one end, a middle hinge member (68) is connected and fixed to the middle, and a bottom hinge member (69) is connected and fixed to the other end, respectively, to, in the width direction, the underside of a deck (2) of a floating pier (1) or of a transom step (2′) of a boat (1′); and a main ladder (20) and guide rails (30) are provided rotatable about the top hinge member (67) via top connecting members (61); and with a bottom latch element (64) being engaged with the bottom end of the main ladder (20) or members in the vicinity thereof, a sliding member (40) is located at the bottom end of the guide rails (30), and all constituting parts are stowed within the width of the deck (2) of the floating pier (1).