The utility model discloses a continuous casting machine backup roll cooling device. The continuous casting machine backup roll cooling device comprises a master pipeline, a plurality of branch pipelines and a plurality of small water spray holes, wherein one end of the master pipeline is sealed, the other end of the master pipeline is a cooling water inlet, one end of each branch pipeline is communicated with the master pipeline, the other end of each branch pipeline is sealed, the small water spray holes are formed in all the branch pipelines respectively, and the branch pipelines are sequentially fixed to a continuous casting machine backup roll frame and are parallel to a backup roll. Each branch pipeline does not make contact with a continuous casting, the temperature is low, cooling water cannot scale, water flows smoothly and water outlets cannot be blocked; a backup roll bearing can be directly cooled outwards so that locking, caused by high temperature, of the roll bearing can be prevented; the continuous casting machine backup roll cooling device can eliminate accumulated slags on the surface of the backup roll while cooling the backup roll, the practicability of the device is strong, disassembly, assembly and operation of the device are simple, convenient and workable, the flexibility of rotation of the continuous casting machine backup roll is improved, and the service life of the roll bearing is prolonged.