A stepless transmitting and speed-varying structure contains a power mechanism to drive a first transmission shaft by using power. The first transmission shaft is connected with a set of disk members including fixed and movable discs. A transmitting mechanism includes a belt disposed on the disk members, with one end of the belt connected with an intermediate speed-varying stem coaxial with a transmitting member to actuate a second transmission shaft. The second transmission shaft includes a resilient member, with one end of the resilient member coupled with the intermediate speed-varying stem and with another end thereof connected with a fixed member. A speed varying mechanism includes the second transmission shaft connected with a variable speed member, an actuated member, and plural eccentric blocks. The variable speed member couples with a connecting rod, with one end of the connecting rod joined with the movable disc.