Abstract: A process for producing an oil-modified resin having a softening point of 40.degree. to 200.degree. C., which comprises reacting [A] an acid-modified cyclopentadiene resin having an acid value of 0.1 to 100 in the presence of [C] at least one metal compound selected from the group consisting of polyvalent metal alcoholates and chelate compounds thereof with [B] an oily modifier containing at least 4 carbon atoms and having a functional group capable of reacting with the metal compound [C], said acid-modified cyclopentadiene resin being selected from the group consisting of (i) the reaction product of 100 parts by weight of a cyclopentadiene resin free from a carboxyl or acid anhydride group, 0 to 200 parts by weight of a higher fatty acid ester containing a conjugated double bond and 0.2 to 50 parts by weight of an .alpha.,.beta.