The invention relates to an automatic collection device and method for waste steel balls and sundries in discharged materials of a ball mill. The collection device comprises a ball mill barrel, a ball mill end cap and a ball mill discharging barrel; and the collecting device is characterized in that a taper drum sieve is fixedly connected to a discharging opening of the ball mill discharging barrel, an ore slurry receiving box is installed under the taper drum sieve, and a waste steel ball and sundry collecting box is installed at an outlet of the taper drum sieve, a plurality of screen holes are evenly distributed on the taper drum sieve, a spiral plate is welded to the inner side wall of the taper drum sieve, and the rotating direction of the spiral plate is opposite to the rotating direction of the ball mill; and a washing water pipe is installed at the middle axis of the taper drum sieve, and a row of thin holes are drilled in the washing water pipe. By means of the automatic collection device and method for the waste steel balls and the sundries in the discharged materials of the ball mill, dressing materials are purified, and the indicators in beneficiation can be effectively improved; and meanwhile, the collected waste steel balls can be recycled for machining and using, and the level of resources utilization is improved.