To provide a resin composite using cellulose nanofibers with a narrow fiber diameter distribution and having a small linear expansion coefficient and excellent transparency, a method for producing the same, and a method for producing cellulose nanofibers for the same.

The resin composite contains cellulose nanofibers, wherein the cellulose nanofibers are a surface-acylated plant-derived cellulose fiber aggregate and have a degree of Iβ crystallization in a range of 40-60%, an average fiber diameter in a range of 4-200 nm and a coefficient of variation (S/Da) which is a ratio between the average fiber diameter Da and its standard derivation S in a range of less than 0.15.