PURPOSE: To have a large gearing ratio without requiring fine adjustment of the ratio and causing large-sized construction by transmitting the peripheral linear speeds of a large dia. part and small dia. part, when rollers are rolling on the fixed internal circumferential surface of a housing, separately through two rotary shafts.

CONSTITUTION: In a transmission according to the present invention, a plurality of rollers 2 are arranged capable of rolling on the fixed interval circumferential surface E provided on the inner wall of a hollow housing 1. That is, each roller 2 is provided at the periphery with a major dia. part C of a dia. dC and a minor dia. part B of a dia. dB in such a manner as consolidated in a single body, wherein the major dia. part C can move in idling in a recess 1a provided on the circumferential surface E while the minor dia. part B is rolling on the circumferential surfaces E on both sides. Accordingly pressure fitting is made to the major and minor dia. parts C, B on the inner circumferential side with an inscribing circle D of a dia. dD and an inscribing circle A of a dia. dA as common inscribing circle, wherein the dia. of these inscribing circles D, A can be expressed as dD=(dO-dC)dA=dO-dB, where dO is orbiting dia. of roller 2 round the axis (m). Rotary shafts 3, 4 can perform power transmission with a certain gearing ratio, when one of them is used as input shaft and the other as output shaft.