An autotetraploid, Sawonppong 28 was derived from a thick-leaf and highly productive mulberry variety, Huyeoprok, by colchicine solution treatment on growing point and its characteristics were as follows. The number of somatic chromosomes of the derived variety was 2n=56 of an autotetraploid and green tip sprouting stage was medium budding variety with triangular oval shape and thick leaves contained rich chlorophyll. The length of branches was comparatively short and the number of branches was also small. However the branches were thick and non-budding length percentage at basal part of branch was high and cold hardiness was weak.