An electric bicycle and a method of controlling the same are disclosed. The electric bicycle according to one embodiment of the present invention includes a weight sensing unit for sensing a rider's weight; a motor output controlling unit for controlling a motor driving output; and an electronic control unit for varying the motor output through the motor output controlling unit according to the weight sensed by the weight sensing unit, and the weight sensing unit classifies the rider's weight into a standard weight mode, an underweight mode, and an overweight mode according to the sensed weight, and if the weight is in the underweight mode, the weight sensing unit reduces the motor output to a value below the motor output for the standard weight mode and if the weight is in the overweight mode, the weight sensing unit increases the motor output to a value above the motor output for the standard weight mode.