The invention provides a fresh seaweed chopping device for achieving free-chopping of foreign bodies. The device is used for chopping and foreign body selection of fresh seaweed. By the aid of the device, fresh seaweed materials are chopped, shapes of foreign bodies are not changed, small seaweed and large foreign bodies are obtained, foreign bodies are separated through a screening slot negative-pressure filtering mode, small seaweed can pass a screening slot easily, large foreign bodies cannot pass the screening slot, foreign bodies and the seaweed can be separated completely, and the separation effect is improved greatly. Besides, the conveyer of the device is in a stepping motion mode, the device is combined with a combined cutter, grains of chopped seaweed materials are uniform, seaweed powder is reduced obviously, and the yield of fresh seaweed materials is improved.