PURPOSE: To obtain paper of increased burst index and improved quality by adding a paper quality-improving agent of a cation-containing polymer prepared by copolymerizing acrylamide and a diallylamine to an aqueous pulp slurry and then making the mixture into paper with no use of a sizing agent.

CONSTITUTION: An aqueous pulp slurry is mixed with a paper quality-improving agent of a cationic group-containing polymer which is prepared by copolymerization of an acrylamide of formula I (R0 is H, methyl) such as acrylamide and a diallylamine of formula II (R1, R2 are H, methyl; HX is acid) such as diallyldimethyl-ammonium chloride in a water-isopropyl alcohol mixed solvent at 55°C for 6 hours in the presence of ammonium persulfate and then making into paper in the absence of a sizing agent to give the objective paper of increased burst index and improved paper quality.