The present invention provides means useful for establishing an excellent isoprene monomer production system. Specifically, the present invention provides a polynucleotide of the following (a), (b), or (c): (a) a polynucleotide comprising (i) the nucleotide sequence represented by SEQ ID NO:1, or (ii) the nucleotide sequence consisting of the nucleotide residues at positions 133 to 1785 in the nucleotide sequence represented by SEQ ID NO:1; (b) a polynucleotide that comprises a nucleotide sequence having 90% or more identity to the nucleotide sequence of (i) or (ii) above, and encodes a protein having an isoprene synthase activity; or (c) a polynucleotide that hybridizes under a stringent condition with a polynucleotide consisting of a nucleotide sequence complementary to the nucleotide sequence of (i) or (ii) above, and encodes a protein having an isoprene synthase activity; and the like.