[Problem]To provide a plant growth promoting agent which is environment-friendly and highly safe [Means to Solve the Problem] Since cellulose nanofibers having a specific average fiber diameter and a specific average fiber length are used as a plant growth promoting material, agglomeration of the cellulose fibers is thereby suppressed to enable efficient insecticidal effect to be realized. As the cellulose nanofibers, there may be mentioned, for example, those derived from cellulose including natural plants such as wood fibers, bamboo fibers, sugarcane fibers, seed hair fibers, leaf fibers and the like.
