The present invention provides a curable resin composition including a bifunctional or more (meth)acrylate compound, indium tin oxide particles, and an acidic polymer, in which the acidic polymer has a moiety including a carboxyl group at a polymer skeleton of a (meth)acrylate compound and at any one of terminals of the polymer skeleton of a (meth)acrylate compound, and an acid value of the acidic polymer is 2.0 mgKOH/g or more and less than 100 mgKOH/g. The curable resin composition of the present invention provides a transparent cured product, hardly causes bubbles to be mixed in a case of applying the curable resin composition to a mold so as to form a lattice-shaped cured product, and also has a good peeled surface shape from the mold after curing. The present invention also provides a diffractive optical element including a surface having a diffraction grating shape and formed of the cured product of the curable resin composition.