A water-based heat fixing ink having at least the following 4 compounds, a: pigment; b: water-soluble resin comprising a copolymer, in which a monomer having a carboxyl group and monomer having a hydrophobic group are polymerized, and the resin is dissolved by neutralization with an amine; c: an organic solvent satisfying following Equation (1) which is represented by a hydrogen bonding term and a polar term of a solubility parameter; and d: water; wherein b is contained in an amount of 2.5-7.0 weight % as a free polymer in a water-based heat fixing ink, 8≦(σp2+σh2)1/2≦12  Equation (1).