It is intended to provide a component promoting the growth of leguminous plants. The present invention provides a promoter for leguminous plant growth comprising a glycoside of soyasapogenol B as an active ingredient, and a method for promoting the growth of a leguminous plant using a glycoside of soyasapogenol B as an active ingredient. The glycoside of soyasapogenol B is a glycoside having a hydroxy group at position C-22 of the soyasapogenol B and having a saccharide bonded to a hydroxy group at position C-3 of the soyasapogenol B.
