The utility model discloses a broccoli seed harvesting device, and relates to the field of seed harvesting, the broccoli seed harvesting device comprises a moving base, a supporting column is mounted on the moving base, the moving base is connected with a mounting seat through the supporting column, a lifting device is mounted on the mounting seat, an adjusting device is arranged on the lifting device, and the adjusting device is connected with the moving base through the supporting column. And a harvesting arm is mounted on the adjusting device. The output end of a driving air cylinder can pull a cross rod to move, the cross rod drives a second supporting rod to move, the upper end of the second supporting rod moves with a second connecting shaft as the center, a moving wheel at the lower end moves in a limiting inner shell, and at the moment, the upper end of the second supporting rod can jack up one end of an upper base; the other end of the upper seat can be jacked up by the first supporting rod through the central shaft, and the height of the harvesting arm at the upper part can be adjusted at the moment, so that the overall harvesting range is expanded.