To provide a resin dispersion having good compatibility with polar resins, excellent in adhesiveness to olefin-based polymers and useful as a surface treating agent, an adhesive, a coating agent and the like.

In the resin dispersion, a modified olefin-based polymer is dispersed in an organic solvent, the modified olefin-based polymer comprises 100 pts.wt. olefin-based polymer (A) and 20-500 pts.wt. polar high molecular compound (B) bonded to the polymer (A) and the organic solvent contains ≥20wt.% polar solvent.