The invention discloses an automatic feeding device capable of operating in the water body. The automatic feeding device comprises an outer cover, a gas storage component located in the outer cover and a stretching component connecting the outer cover with the gas storage component; the automatic feeding device is characterized in that the outer cover is made of flexible material, the gas storagecomponent is of a double-sleeve type accommodating cavity formed by an inner wall and an outer wall, the accommodating cavity formed by the inner wall and the outer wall of the gas storage component is a storage part, the inner wall of the gas storage component is made of sealed elastic material, and one end of the gas storage component is provided with an air inlet. By the arrangement, automaticfeeding in different positions of the water body is realized.