PROBLEM TO BE SOLVED: To provide a device and method for reduction of shellfish poisoning in which the introduction is made easy even for a small fisherman.SOLUTION: A device for reduction of shellfish poisoning according to the present invention includes: an upper cover part 51 receiving shellfishes 1 of an aquaculture or growth target and covering an upper part of a plurality of aquaculture baskets 3 connected in multistage； a peripheral cover part 52 covering the side face of the plurality of aquaculture baskets 3； and an opening part 53 opening the bottom side of the plurality of aquaculture baskets 3. Fine joints of the upper cover part 51 and the peripheral cover part 52 can prevent invasion of toxic plankton. The plurality of aquaculture baskets 3 are connected in multistage in the direction from the water surface to the bottom. The upper part and the periphery of the plurality of aquaculture baskets 3 connected in multistage are covered by a cover 55 formed of the upper cover part 51 and the peripheral cover part 52.
