A rotation transmission mechanism, comprising: an internal rotation member inserted by a rotating shaft; and an external rotation member configured on the internal rotation member in a free rotation manner, wherein: the internal rotation member comprises: a disc-shaped internal rotation member body having through holes for inserting the rotating shaft; and one or more outer circumferential convex parts, integrally formed with the internal rotation member body (3 a) or fixedly arranged on the internal rotation member body (3 a), and protruding to an outer circumferential side of the internal rotation member body (3 a); the external rotation member comprises: a side plate part, located in a side position of the outer circumferential convex parts of the internal rotation member and inserted into the convex part of the internal rotation member in a free rotation manner, a circular ring part configured on the internal rotation member at an outer side of the outer circumferential convex parts of the internal rotation member in a free rotation manner; and one or more inner circumferential convex parts, integrally formed with the circular ring part in a manner of protruding to an inner circumferential side of the circular ring part or fixedly arranged on the circular ring part, and configured alternately with the outer circumferential convex parts of the internal rotation member; elastic parts are configured between the outer circumferential convex parts and the inner circumferential convex parts on a rotation direction side of the advancing outer circumferential convex parts; and when the internal rotation member and the external rotation member rotate, the elastic parts are clamped between the outer circumferential convex parts and the inner circumferential convex parts and generate elastic deformation, characterised by that the external rotation member further comprises a cover part, inserted into the convex part in a free rotation manner in a state of being configured oppositely to the side plate part and fixed to the circular ring part through screws and wherein in the rotation transmission mechanism, the outer circumferential convex parts are formed in such a manner that a surface on the rotation direction side is greater than a surface on an opposite side of the rotation direction; and the outer circumferential convex parts are formed in such a manner that the surface on the rotation direction side is inclined more gently than the surface on the opposite side of the rotation direction, and a fillet is formed on a boundary part between the surface on the rotation direction side and the internal rotation member body; and bearing balls (3g, 3h, 18g, 18h) are rotatably kept on surfaces and backs of the outer circumferential convex parts and respectively rolled and simultaneously rotated on the cover part and the side plate. the internal rotation member comprises: a disc-shaped internal rotation member body having through holes for inserting the rotating shaft; and one or more outer circumferential convex parts, integrally formed with the internal rotation member body (3 a) or fixedly arranged on the internal rotation member body (3 a), and protruding to an outer circumferential side of the internal rotation member body (3 a); the external rotation member comprises: a side plate part, located in a side position of the outer circumferential convex parts of the internal rotation member and inserted into the convex part of the internal rotation member in a free rotation manner, a circular ring part configured on the internal rotation member at an outer side of the outer circumferential convex parts of the internal rotation member in a free rotation manner; and one or more inner circumferential convex parts, integrally formed with the circular ring part in a manner of protruding to an inner circumferential side of the circular ring part or fixedly arranged on the circular ring part, and configured alternately with the outer circumferential convex parts of the internal rotation member; elastic parts are configured between the outer circumferential convex parts and the inner circumferential convex parts on a rotation direction side of the advancing outer circumferential convex parts; and when the internal rotation member and the external rotation member rotate, the elastic parts are clamped between the outer circumferential convex parts and the inner circumferential convex parts and generate elastic deformation, characterised by that the external rotation member further comprises a cover part, inserted into the convex part in a free rotation manner in a state of being configured oppositely to the side plate part and fixed to the circular ring part through screws and wherein in the rotation transmission mechanism, the outer circumferential convex parts are formed in such a manner that a surface on the rotation direction side is greater than a surface on an opposite side of the rotation direction; and the outer circumferential convex parts are formed in such a manner that the surface on the rotation direction side is inclined more gently than the surface on the opposite side of the rotation direction, and a fillet is formed on a boundary part between the surface on the rotation direction side and the internal rotation member body; and bearing balls (3g, 3h, 18g, 18h) are rotatably kept on surfaces and backs of the outer circumferential convex parts and respectively rolled and simultaneously rotated on the cover part and the side plate.