The present invention relates to a method of producting corosolic acid by using plant cells that produce corosolic acid. More particularly, the present invention relates to a method of producting corosoilic acid by using plant cell suspension cultures comprising the steps of: inducing a callus from a tissue of a plant producing corosolic acid; preparing a cell line capable of being cultured in liquid culture medium from the induced callus; culturing the cell line in a suspension culture; and isolating corosolic acid from the culture solution. The present invention has advantage of maximizing productivity by utilizing two-stage culture, treatment with inducing agent, and high cell-density culture in the suspension culture of plant cells producing corosolic acid.