To obtain hot water-resistant sizing paper by making paper from a pulp slurry by using a reaction product of a rosin-based material containing hydrogenated rosin with an α,β-unsaturated acid.

An aqueous emulsion of a reaction product is prepared by adding an α,β-unsaturated acid such as maleic acid or fumaric acid in an amount of 5-15wt.% of a rosin-based material to the rosin-based material containing ≥5wt.% hydrogenated rosin, or by adding an α,β-unsaturated acid to a rosin- based material other than a hydrogenated rosin, mixing ≥5wt.% hydrogenated rosin and making an adding amount of the unsaturated acid 5-15wt.% based on the rosin-based material containing hydrogenated rosin. The objective hot water-resistant sizing paper is obtained by using the aqueous emulsion and subjecting a pulp slurry to papermaking within a range of pH 5.0-7.5.