A motor torque transmission device, comprising: an electric motor that generates motor torque; and a reduction-transmission mechanism that reduces a speed of rotation output from the electric motor, and that transmits driving force to a driving force transmission target, the reduction-transmission mechanism being a speed reduction mechanism, comprising: a speed reduction unit that includes an input member (50, 51) having external gear teeth (50c, 51c) that makes circular motion about a rotation axis with a predetermined eccentric amount (δ), and a rotation force applying member having internal gear teeth, the number (Z 3) of which is larger than the number (Z 1, Z 2) of teeth of the input member (50, 51) and that is in mesh with the input member (50, 51); and a lubricating oil supply unit that supplies lubricating oil to a bearing (54, 55) of the speed reduction unit, wherein the lubricating oil supply unit includes an oil tank arranged outside of the rotation force applying member, an oil delivery passage (61, 62) that delivers the lubricating oil from a space (C, C'), formed between the input member (50, 51) and the rotation force applying member, to the oil tank, and a first oil introduction passage that introduces the lubricating oil from the oil tank to the bearing (54, 55), and the lubricating oil is delivered from the space to the oil delivery passage (61, 62) through pumping action of the input member (50, 51) based on the circular motion, characterized in that the electric motor has a motor shaft and an eccentric portion (42a, 42b) is provided on the motor shaft, the eccentric portion (42a, 42b) having an axis (O 1, O 2) that is offset from an axis of the motor shaft; and in the reduction-transmission mechanism, the lubricating oil supply unit supplies the lubricating oil to an input-side bearing (54, 55) which serves as the bearing (54, 55) and via which the input member (50, 51) is rotatably supported by the eccentric portion (42a, 42b). an electric motor that generates motor torque; and a reduction-transmission mechanism that reduces a speed of rotation output from the electric motor, and that transmits driving force to a driving force transmission target, the reduction-transmission mechanism being a speed reduction mechanism, comprising: a speed reduction unit that includes an input member (50, 51) having external gear teeth (50c, 51c) that makes circular motion about a rotation axis with a predetermined eccentric amount (δ), and a rotation force applying member having internal gear teeth, the number (Z 3) of which is larger than the number (Z 1, Z 2) of teeth of the input member (50, 51) and that is in mesh with the input member (50, 51); and a lubricating oil supply unit that supplies lubricating oil to a bearing (54, 55) of the speed reduction unit, wherein the lubricating oil supply unit includes an oil tank arranged outside of the rotation force applying member, an oil delivery passage (61, 62) that delivers the lubricating oil from a space (C, C'), formed between the input member (50, 51) and the rotation force applying member, to the oil tank, and a first oil introduction passage that introduces the lubricating oil from the oil tank to the bearing (54, 55), and the lubricating oil is delivered from the space to the oil delivery passage (61, 62) through pumping action of the input member (50, 51) based on the circular motion, characterized in that the electric motor has a motor shaft and an eccentric portion (42a, 42b) is provided on the motor shaft, the eccentric portion (42a, 42b) having an axis (O 1, O 2) that is offset from an axis of the motor shaft; and in the reduction-transmission mechanism, the lubricating oil supply unit supplies the lubricating oil to an input-side bearing (54, 55) which serves as the bearing (54, 55) and via which the input member (50, 51) is rotatably supported by the eccentric portion (42a, 42b). a speed reduction unit that includes an input member (50, 51) having external gear teeth (50c, 51c) that makes circular motion about a rotation axis with a predetermined eccentric amount (δ), and a rotation force applying member having internal gear teeth, the number (Z 3) of which is larger than the number (Z 1, Z 2) of teeth of the input member (50, 51) and that is in mesh with the input member (50, 51); and a lubricating oil supply unit that supplies lubricating oil to a bearing (54, 55) of the speed reduction unit, wherein the lubricating oil supply unit includes an oil tank arranged outside of the rotation force applying member, an oil delivery passage (61, 62) that delivers the lubricating oil from a space (C, C'), formed between the input member (50, 51) and the rotation force applying member, to the oil tank, and a first oil introduction passage that introduces the lubricating oil from the oil tank to the bearing (54, 55), and the lubricating oil is delivered from the space to the oil delivery passage (61, 62) through pumping action of the input member (50, 51) based on the circular motion, characterized in that the electric motor has a motor shaft and an eccentric portion (42a, 42b) is provided on the motor shaft, the eccentric portion (42a, 42b) having an axis (O 1, O 2) that is offset from an axis of the motor shaft; and in the reduction-transmission mechanism, the lubricating oil supply unit supplies the lubricating oil to an input-side bearing (54, 55) which serves as the bearing (54, 55) and via which the input member (50, 51) is rotatably supported by the eccentric portion (42a, 42b).