The objective of the present invention is to provide an accommodation ladder fixing device, which more firmly and safely fixes, to an exterior wall of a ship, an accommodation ladder temporally provided so as to allow pilots to safely board and disembark the ship. That is, the present invention comprises: a housing (10), which has a fixing plate (13) formed at the rear end thereof to be mounted on the accommodation ladder (100), has a fixing box (11), of which the front side is opened, formed on the fixing plate (13), and has hinge shafts (15) formed at both sides of a through-hole (14) of the fixing box (11); an attachment/detachment means (20), which has a movable block (21) insertively provided so as to be movable forward and rearward to/from the fixing box (11), and a magnetic member (22) attached/detached to/from the exterior wall of a hull (200) and provided at the front end of the movable block.