Abstract: A ladder safety device (2) for removably securing a ladder (40) to a parapet wall (36) of a rooftop (38), including: a pair of support clamps (4) securable to the parapet wall (36), each said support clamp (4) including a first support member (10), a second support member (12), and an extended arm (14) joining said first support member (10) to said second support member (12), wherein a distance between said support members (10, 12) defines a width adjustable to the width of the parapet wall (36); an elongate plate (6) connecting said pair of support clamps (4) to each other; and at least one ladder hook (8) extending from said elongate plate (6) for securely receiving a rung of the ladder (40).