This invention provides an automobile water-based paint capable of forming coating film of little metallic mottling and excellent flip-flop property and smoothness, which comprises hydroxyl-containing resin, viscosity-regulating agent and hydrophobic solvent, the viscosity-regulating agent being a copolymer obtained by copolymerizing a monomeric mixture containing a (meth)acrylic acid (salt), monomer represented by the following formula (1) [in which R1 stands for hydrogen or methyl, R2 and R3 stand for hydrogen, methyl or ethyl, R4 stands for C8-24 hydrocarbon group, and n is an integer of 3-60], alkyl (meth)acrylate of which alkyl moiety has 1-4 carbons and a monomer having at least two polymerizable unsaturated groups per molecule, at specific ratios.