The invention provides a full-automatic adjustable steel-pipe cutting device which comprises a workbench, a mounting frame, a first support, a second support, a first cutting mechanism and a second cutting mechanism. A plurality of cutting grooves are formed in the workbench in the Y direction. The first support and the second support are mounted on the mounting frame and can move in the Z direction. The first cutting mechanism comprises a first base, a first mounting plate and a first cutting unit. The two ends of the first base are mounted on the first support and the second support respectively. The first mounting plate is mounted on the first base. The first cutting unit is mounted on the first mounting plate and used for cutting steel pipes. The second cutting mechanism comprises a second base, a second mounting plate and a second cutting unit. The two ends of the second base are mounted on the first support and the second support respectively. The second mounting plate is mounted on the second base. The second cutting unit is mounted on the second mounting plate and used for cutting the steel pipes. The full-automatic adjustable steel-pipe cutting device is capable of cutting multiple steel pipes at a time, good in cutting effect and high in production efficiency.