NOVELTY - A low-temperature fluidity improver contains aromatic-type compound (I) and compound (B). Compound (B) is ethylene-vinylacetate copolymer, ethylene-vinyl propionate copolymer, ethylene-vinyl butyrate copolymer, ethylene-2-ethylhexyl vinyl copolymer, ethylene-2-ethylhexyl vinyl-vinyl acetate copolymer, styrene-maleate copolymer, styrene-fumarate copolymer, polyalkyl acrylate, polyalkyl methacrylate, alkenyl succinic acid amide, alkenyl succinimide, isophthalic acid compound (II), terephthalic acid compound (III), and/or diketone compound (IV).    USE - Low-temperature fluidity improver is used for biodiesel fuel composition (claimed) e.g. gasoline, light oil and petroleum for motor vehicles.    ADVANTAGE - The low-temperature fluidity improver efficiently improves the fluidity of biodiesel fuel.    DETAILED DESCRIPTION - A low-temperature fluidity improver contains aromatic-type compound (I) and compound (B). The compound (B) is ethylene-vinylacetate copolymer, ethylene-vinyl propionate copolymer, ethylene-butyrate vinyl copolymer, ethylene-2-ethylhexyl vinyl copolymer, ethylene-2-ethylhexyl vinyl-vinyl acetate copolymer, styrene-maleate copolymer, styrene-fumarate copolymer, polyalkyl acrylate, polyalkyl methacrylate, alkenyl succinic acid amide, alkenyl succinimide, isophthalic acid-type compound of formula (II), terephthalic acid-type compound of formula (III), and/or diketone-type compound of formula: X-(C(=O)-R15-C(=O)-O-R16-O)s-Y'(IV).    R1-R6=H or 1-4C alkyl;    R7-R14=H or 8-22C hydrocarbyl optionally contains oxygen and/or nitrogen, and R7 and R8, R9 and R10, R11 and R12, R13 and R14 are not simultaneously hydrogen;    m=0 or 1;    n=1-3;    t=0 or 1;    R15=2-300C hydrocarbyl;    R16=2-500C hydrocarbyl optionally contains oxygen and nitrogen;    s=5-500;    X=OH or HO-R16-O-;and    Y'=H or -CO-R15-COOH.    When t=0, then R13 is H. An INDEPENDENT CLAIM is included for biodiesel fuel composition, which contains 0.05-10 %mass of aromatic-type compound of low temperature fluidity improver.