A modified liquid diene-based rubber (A) including, in a molecule, a modified group (a) containing a (meth)acryloyl group as a part thereof and at least one modified group (b) selected from a dicarboxylic acid monoester and a dicarboxylic acid monoamide, with the proviso that the modified group (b) comprises no (meth)acryloyl group as a part thereof, wherein the functional group equivalent weights of the modified group (a) and the modified group (b) are each in the range of 700 to 40,000 g/eq. Also provided is a curable resin composition containing the modified liquid diene-based rubber.