Abstract: A cycloid reduction gear for a wind force generator is provided. The wind force generator having generation blades and horizontal and vertical axes includes: a horizontal-axis reduction gear provided in a direction perpendicular to the vertical axis to rotate the generation blades in a horizontal direction; and a horizontal-axis rotation ring gear installed at the vertical axis and internally contacting with the horizontal axis reduction gear to rotate the vertical axis in a horizontal direction according to a rotation of the horizontal axis reduction gear. Thereby, the horizontal axis of the wind force generator can rotate according to a wind direction, and by combining and installing a reduction gear and a cycloid disk in the wind force generator, the horizontal axis moves in an appropriate reduced ratio and thus the wind force generator can stably operate according to a wind direction.