Infinitely variable speed drive device

The invention relates to the technical field of vehicle drive, in particular to an infinitely variable speed drive device and a drive shaft with good impact performance and mechanical performance in an infinitely variable speed drive system. The drive shaft comprises a step-shaped shaft body; the shaft body sequentially comprises a connection component section connected with a power output portion, a support section connected with a support component, a shaft body solid section connected with any other components, a transition section between the shaft body solid section and a flange section at the rightmost end, and the flange section located at the rightmost end and connected with a power input portion from left to right. The invention further provides a machining method for the drive shaft, and the machining method can reduce cost, simplify the procedures and improve the quality of finished products.