The invention discloses a power generation device using an automobile brake. The power generation device comprises at least one pair of friction wheels (1) which are symmetrically arranged, a hydraulic braking transmission, transmission mechanisms and a generator (5), wherein the hydraulic braking transmission is connected between rotating shafts (2) of the pair of friction wheels (1) and drives a brake hub of the friction wheel and the wheel to engage/disengage; the transmission mechanisms are connected with the rotating shafts (2) of the friction wheels respectively; and the generator (5) is connected with the output shafts of the transmission mechanisms. The forward kinetic energy is converted into electric energy during automobile brake, then used to charge a storage battery and finally used by the automobile. The aims of energy conservation, consumption reduction and low carbon tour are effectively fulfilled. The power generation device conforms to the current tendency of social energy conservation and emission reduction and environmental protection, and has good market prospect.