PURPOSE: To efficiently create an artificial haploid plant useful for creation of new varieties by removing stamens from a flower bud of a seed plant, applying brasinosteroids to the flower bud, growing an ovary in a plant body or taking out the ovary from the plant body and culturing the ovary.

CONSTITUTION: Stamens are removed by a pincette from a flower bud within 1 day before blooming of a seed plant (e.g. Arabidopsis thaliana) and 0.1ppm aqueous solution of brassinosteroids is applied from fine tip of a pipet to a stigma after one day after blooming of this flower bud and an ovary is reared together with the plant body or the ovary is taken out from the plant body and cultured. Thereby, the objective artificial haploid plant on which chemical mutagen such as nitorosoguanidine effectively acts is efficiently produced in a short period using brassinosteroids which are safe to handle. Furthermore, plants to which this method is applicable are grains such as rice, wheat, soybean or corn, vegetables such as cucumber, tomato or Chinese cabbage and fruit trees such as orange, apple, pear or grape.