To provide a density-reducing agent for paper, which produces low-density paper having excellent low density, slight reduction in sizing degree and slight reduction in strength: and to provide a method for producing low-density paper.

The density-reducing agent for paper includes an amino compound diester represented by general formula [1] (wherein R1 is 1-4C alkyl; R2 and R3 are each independently 7-35C alkyl, hydroxyalkyl, alkenyl or hydroxyalkenyl; A1O and A2O are each independently 2-4C oxyalkylene; k is a number of not less than 1, m is a number of not less than 2 and k+m is a number of 3-40; and when a plurality of A1Os exist, the plurality of A1Os each may be the same or different and a plurality of A2Os may be the same or different) or its salt. The method for producing low-density paper includes adding the amino compound diester represented by general formula [1] or its salt to pulp useful for papermaking.