<p>Disclosed are a papermaking method of preparing a paper having a reinforced strength wherein a polymer latex is added to a paper stock in an amount of from 2.5 to 30 % by weight. The polymer latex is prepared by neutralizing a seed polymer with an acid or a salt or by quaternizing it with a quaternizing agent. The surfaces of the emulsion grains are highly densely cationated. The seed polymer is formed by adding a monomer as represented by the following formula (I) or a mixture of the monomer (I) and copolymerizable ethylenic unsaturated monomer(s) (II) to a seed latex of a carboxyl-modified synthetic rubber latex or synthetic resin emulsion and polymerizing them: <CHEM> R1 represents H or CH3; R2 represents an alkylene group having from 2 to 5 carbon atoms; R3 and R4 each represent H or an alkyl group having from 1 to 5 carbon atoms; A represents - @-O- or -@-NH-; and R1, R3 and R4 and so selected that the monomer is hardly soluble or insoluble in water. The paper has a noticeably improved paper-strength.</p>
