A gear-shifting structure is provided for a vehicle. The vehicle includes a transmission box that contains therein a gear train, a clutch, a switching fork, a gear-shifting hub, and a motor. The motor cooperates with a worm shaft to actuate the clutching operation of the clutch and to cause movement of the gear-shifting hub in order to carry out the gear shifting operation. The motor has a rotary member that drives the worm shaft on which a worm and a cam are mounted. To effect gear shifting, the motor drives the worm shaft to have the cam abut and displace the clutch and at the same time, the worm drives the gear-shifting hub to thus realize the operation of gear shifting.