A conjugate cam reducer includes input and output units disposed at two opposite sides of a transmission unit along an output axis. The transmission unit includes input-side and output-side cam discs having first and second grooved surfaces. The input unit includes an input disc having a plurality of first receiving grooves registered with the first grooved surfaces to receive input rollers, and an eccentric shaft rotated to drive rotation of the transmission unit in an eccentric cam motion. The output unit includes an output disc having an inner peripheral wall which engages with the output-side cam disc, and a plurality of second receiving grooves which are registered with the second grooves to receive output rollers. An outer diameter of each first toothed surface and an outer diameter of each second toothed surface is gradually increased along a direction parallel to the output axis.

A conjugate cam reducer includes input and output units disposed at two opposite sides of a transmission unit along an output axis. The transmission unit includes input-side and output-side cam discs having first and second grooved surfaces. The input unit includes an input disc having a plurality of first receiving grooves registered with the first grooved surfaces to receive input rollers, and an eccentric shaft rotated to drive rotation of the transmission unit in an eccentric cam motion. The output unit includes an output disc having an inner peripheral wall which engages with the output-side cam disc, and a plurality of second receiving grooves which are registered with the second grooves to receive output rollers. An outer diameter of each first toothed surface and an outer diameter of each second toothed surface is gradually increased along a direction parallel to the output axis.