To obtain a tackifying resin capable of imparting an excellent adhesive force and having excellent weather resistance by using a rosin substance containing tetrahydroabietic acid in a specific amount and/or its esterification product.

This tackifying resin comprises (A) a rosin substance containing tetrahydroabietic acid in an amount of ≥50 wt.%, preferably ≥80 wt.%, and/or a rosin ester derived from the component A. The component A is obtained, for example, by hydrogenating a rosin of raw material, such as gum rosin, in the presence of a hydrogenation catalyst under pressurization using hydrogen with heating until the tetrahydroabietic acid content of the hydrogenated rosin reaches ≥50%. In order to improve the color tone of the component A, it is preferable to carry out a distillation purification treatment after the hydrogenation treatment. The component B is obtained by esterifying the component A with a polyhydric alcohol.