The invention relates to a reusable pulling-out device for a steel casing of a bored cast-in-place pile in water. The reusable pulling-out device comprises the two-piece-type steel casing, wherein theopening surfaces of the two-piece-type steel casing are attached and form a cylinder-shaped structure; a plurality of connecting polished rods are equally distributed at the attached positions of openings of the two-piece-type steel casing; the rod bodies are fixedly connected with the outer wall of the two-piece-type steel casing correspondingly; dismounting pull rods are arranged between the openings of the two-piece-type steel casing; and the dismounting pull rods are arranged in the length direction of the openings of the two-piece-type steel casings, the dismounting pull rods are provided with dismounting heads, the rod ends of the dismounting pull rods are connected with pulling-out mechanisms, the pulling-out mechanisms drive the dismounting pull rods to vertically move upwards, and the dismounting pull rods moves upwards and enables the dismounting heads to link the polished rods and separate from the outer wall of the two-piece-type steel casing. The pulling-out device can conveniently realize the repeated utilization of the steel casing and the pulling-out operation of the steel casing.