PURPOSE: To obtain a transformed common periwinkle (Vinca minor) having high proliferability and exhibiting vigorous growth of root even in the absence of plant hormones by transforming the plant with a hairy root inducing gene.

CONSTITUTION: For example, a bacterial cell of the genus Agrobacterium containing a hairy root inducing plasmid (Ri plasmid) is directly inoculated to a tissue piece, etc., of common periwinkle and the obtained transformed cell is cultured in a plant tissue cultivation medium such as Murashige-Skoog medium. The hairy root induced by this process is regenerated to obtain the objective plant. Preferably, the medium is incorporated with 0.01-20mg of auxins to promote the induction of the hairy root or 0.01-20mg of cytokinins to culture the hairy root and remarkably proliferate the developed shoot.