An automatic detergent feeding device includes a liquid storage box, the liquid storage box is provided with a liquid outlet channel, the inside of the liquid outlet channel is provided with an opening and closing valve assembly for opening/closing the liquid outlet channel and an anti-backflow valve assembly for preventing an external liquid from flowing backwards into the liquid storage box, and the anti-backflow valve assembly is arranged at the upstream, corresponding to a liquid outlet direction, of the opening and closing valve assembly. The automatic detergent feeding device is provided with the anti-backflow valve assembly to prevent the external liquid from flowing backwards into the liquid storage box. Therefore, in case of failure of an extraction unit, the anti-backflow valve assembly will close the liquid outlet channel of the liquid storage box to prevent the external liquid from flowing backwards into the liquid storage box to cause water overflow.