Provided is a method for producing a polyisoprenoid, which can increase natural rubber production by enhancing the rubber synthesis activity of rubber particles. The present invention provides methods for producing a polyisoprenoid using a gene coding for a cis-prenyltransferase (CPT) family protein, a gene coding for a Nogo-B receptor (NgBR) family protein and a gene coding for a rubber elongation factor (REF) family protein, specifically a method for producing a polyisoprenoid in vitro using rubber particles bound to proteins coded for by these genes, and a method for producing a polyisoprenoid in vivo using a recombinant organism (plant) having these genes introduced therein.