PURPOSE: To provide a neutral sizing composition for making paper, satisfying both the sizing effect and high burst index simultaneously without any adverse effect on the burst index of the sized paper by adding a prescribed amount of a specific ester to a succinic anhydride substituted with a hydrocarbon.

CONSTITUTION: (A) An ester of formula I (R1 is 7 to 21C alkyl which may bear a hydroxyl group, alkenyl; R2 is 1 to 22C alkyl, alkenyl; (m) is an integer of 2 to 4; (n) is a number 4 from 5 to 30) is added to (B) a succinic anhydride substituted with a hydrocarbon of formula II (R is 8 to 30C alkyl, alkenyl) at a (2-25)/100 weight ratio of A/B to give the objective neutral sizing composition for paper having very high practical value because it has excellent sizing effect, satisfies simultaneously both the sizing effect and the high burst index without adverse effect on the burst index of the sized paper.