Disclosed herein are a promoter (SEQ ID NO.: 1) inducing high level expression of a target gene in plant tissue cultured cells, derived from the sweetpotato gene of Ran GTPase, small GTP binding protein, a plant transformation vector for carrying the same and a method for expressing a foreign gene in plant cell using the vector. The activity of promoter according to the present invention is higher than that of universal CaMV 35S promoter in transgenic suspension cultured cell lines, calluses and adventitious roots. Thus, the promoter is useful in the generation of transgenic cell lines including cultured roots to produce valuable materials such as medicinal or industrial proteins in a large quantities with plant tissue cultured cells.