A method for inducing flowering comprising the step of injecting into a plant body (i) any one of proteins - below: a purified protein comprising the amino acid sequence represented by SEQ ID NO:2; a purified protein comprising an amino acid sequence having deletion, substitution and/or addition of one or several amino acids in the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; and a purified protein comprising an amino acid sequence having an identity of 60% or more with the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; or (ii) a purified protein encoded by a gene comprising any one of DNAs (a)-(c) below: (a) DNA consisting of the nucleotide sequence represented by SEQ ID NO:1 (b) DNA that hybridizes with DNA consisting of a nucleotide sequence complementary to the nucleotide sequence represented by SEQ ID NO:1 under stringent conditions and that codes for a protein having a flowering-inducing activity; and (c) DNA comprising a nucleotide sequence having an identity of 60% or more with the nucleotide sequence represented by SEQ ID NO:1 and coding for a protein having a flowering-inducing activity. (i) any one of proteins - below: a purified protein comprising the amino acid sequence represented by SEQ ID NO:2; a purified protein comprising an amino acid sequence having deletion, substitution and/or addition of one or several amino acids in the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; and a purified protein comprising an amino acid sequence having an identity of 60% or more with the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; or a purified protein comprising the amino acid sequence represented by SEQ ID NO:2; a purified protein comprising an amino acid sequence having deletion, substitution and/or addition of one or several amino acids in the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; and a purified protein comprising an amino acid sequence having an identity of 60% or more with the amino acid sequence represented by SEQ ID NO:2 and having a flowering-inducing activity; or (ii) a purified protein encoded by a gene comprising any one of DNAs (a)-(c) below: (a) DNA consisting of the nucleotide sequence represented by SEQ ID NO:1 (b) DNA that hybridizes with DNA consisting of a nucleotide sequence complementary to the nucleotide sequence represented by SEQ ID NO:1 under stringent conditions and that codes for a protein having a flowering-inducing activity; and (c) DNA comprising a nucleotide sequence having an identity of 60% or more with the nucleotide sequence represented by SEQ ID NO:1 and coding for a protein having a flowering-inducing activity. (a) DNA consisting of the nucleotide sequence represented by SEQ ID NO:1 (b) DNA that hybridizes with DNA consisting of a nucleotide sequence complementary to the nucleotide sequence represented by SEQ ID NO:1 under stringent conditions and that codes for a protein having a flowering-inducing activity; and (c) DNA comprising a nucleotide sequence having an identity of 60% or more with the nucleotide sequence represented by SEQ ID NO:1 and coding for a protein having a flowering-inducing activity.