Method and apparatus for controlling speed of autonomous vehicle

An apparatus for controlling a speed of an autonomous vehicle, includes: a sensor unit for measuring a speed of a wheel of the vehicle; a control unit for controlling the speed of the vehicle by generating a driving signal or a braking signal; and a torque applying unit for applying wheel torque to the wheel based on the driving signal or the braking signal. The control unit is configured to calculate a slip ratio based on the speed of the wheel, determine a road surface condition based on the wheel torque and the slip ratio, determine a maximum speed of the vehicle based on the road surface condition, and control the speed of the vehicle not to exceed the maximum speed. The road surface condition is classified according to a friction coefficient of the road surface, and the wheel torque is braking torque or driving torque applied to the wheel.