Disclosed is a technique for largely increasing the amount of a plant biomass and imparting salt stress tolerance.A gene encoding a protein is introduced, wherein the protein contains a consensus sequence comprising the amino acid sequence depicted in SEQ ID NO:3 and a consensus sequence comprising the amino acid sequence depicted in SEQ ID NO:2 in this order from the N-terminal side, and has a coiled-coil structure, a nucleic acid-binding site, and a leucine-rich repeat structure. Alternatively, an expression control region for the gene which is present endogenously is modified.
