In this study, we propose a high ratio involute gear reducer using the Vernier effect, so-called Vernier drive. Our design consists of a fixed internal gear, a rotating internal gear, and single-profile planetary gears which are mounted on a carrier and simultaneously mesh with both internal gears. Since the mechanism requires a design beyond the conventional gear meshing principles, a method to modify the tooth profile of the rotating internal gear is introduced and mathematically verified with exact geometric relations. The performance of the Vernier drive is theoretically studied by quasi-static analysis, and the operation is tested with additively manufactured prototypes. The results demonstrate that the Vernier drive is able to cover a wide range of reduction ratios with a simple mechanism.