<p>Disclosed is a cold flow improver which can improve the low-temperature flow properties of a biodiesel fuel efficiently. The cold flow improver is characterized by comprising a polymer containing 50 mass% or more of a polyester in the molecule, wherein the polyester is a product of the reaction between a compound represented by general formula (1)[wherein AH2 represents a hydrocarbon group having 2 to 300 carbon atoms; and g represents an average polymerization degree and is a number of 1 to 1000] and/or general formula (2) [wherein AH2 represents a hydrocarbon group having 2 to 300 carbon atoms; and h represents an average polymerization degree and is a number of 1 to 1000] with at least one polyhydric alcohol (Y) represented by general formula (3) (Y) R-(OH) n (3) [wherein R represents an oxygen atom, or a hydrocarbon group having 2 to 500 carbon atoms which may contain a nitrogen atom; and n represents a number of 2 or greater].</p>
