The invention relates to the field of seed coating and discloses a seed coating device which comprises a stirring mechanism, a powder spraying mechanism, an inner container and an outer container, each of the inner container and the outer container is of a hollow structure, the undersurface of each of the inner container and the outer container is a plane, the inner container sleeves in the outercontainer, the undersurface of the inner container is provided with permeation holes, a frustum-shaped boss is arranged on the inner wall of the undersurface of the outer container, a floating plate is arranged between the bottom of the inner container and the outer container, a liquid incoming hole matched with the boss is formed in the floating plate, and the peripheral edge of the floating plate and the inner wall of the outer container are in sliding seal; a strip-shaped through groove is formed in the side wall of the outer container in the height direction of the outer container, a sliding plate is slidably connected in the through groove, and the sliding plate and the inner wall of the through groove form sliding seal; a liquid incoming valve is arranged on the undersurface of the outer container and communicated with the inside of the outer container, the stirring mechanism and the powder spraying mechanism are mounted in the Inner container, and the powder spraying mechanism comprises a nozzle used for spraying powder and facing the undersurface of the inner container. The seed coating device can form uniform coatings on the surfaces of seeds.