The K-Ar ages of biotites, obtained from thirteen pelitic schists in the Jeungpyeong-Deokpyeong area, central Ogcheon metamorphic belt, range from 89 Ma to 213 Ma except for one specimen. These K-Ar ages systematically decrease as the distance between the analyzed specimen and the Jurassic or Creataceous granite decreases. The K-Ar ages of b~otites adjacent to the Jurassic and Cretaceous granites are 166 Ma and 89 Ma, respectively. Thus, the biotite ages are interpreted to result from the partial or complete resetting by thermal activities in association with the intrusion of Mesozoic granites, following the regional-thermal metamorphism at Late Triassic to Early Jurassic times.