This application belongs to the technical field of electric bicycles, and specifically relates to a continuously variable transmission device for a hub motor, including a main shaft, a motor assembly, a hub, a planetary gear set assembly and a flywheel. The hub, the planetary gear set assembly and the flywheel are sequentially sleeved on the main shaft. The planetary gear set assembly includes at least a first planetary gear set and a second planetary gear set connected to each other along an axial direction of the planetary gear set assembly. One end of a sun gear of the first planetary gear set extends into the hub and connected to the motor assembly. One end of planet carrier of the first planetary gear set is connected to the hub, and its another end is connected to the sun gear of the second planetary gear set. One end of planet carrier of the second planetary gear set is connected to its planet gear, and its another end is connected to the flywheel. In this application, power of the flywheel and the motor is coupled and output to the wheel through the hub, which realizes functions of power assist and continuously variable transmission and can achieve a large speed ratio and enable the motor assembly to run at a high speed with low torque, thereby facilitating lightweight design of the mechanism.