Present studies were carried out to produce tetraploid plants by colchicine treatment using seeds, seedlings and shoot tips of Platycodon grandiflorum in Campanulaceae. The most successful colchicine treatment for tetraploid production in P. grandiflorum was soaking treatment using 0.01 and 0.5% colchicine solution for 1 hour and 12 hours, respectively. Morphological characteristics of both diploid and tetraploid were similar, but tetraploid plants had more leaves. Compared to diploid, tetraploid had the larger stomata, but less number of stomata. Fresh weight of tetraploids was 20∼40% heavier than that of diploid.