An improved structure of a rear bicycle brake comprised of two brake arms pivoted respectively with their axes to a bicycle seat tube; both lower sections of axes extending in symmetric to define a clamping part fixed with a brake block to clamp the rim of the rear wheel characterized by that the upper section of the primary brake arm extending at an inclination to form a pull arm; and that of the second brake arm extending in a curve to form a press arm; a slant end opening at the secondary brake arm for the inner cord of the brake cable to penetrate through, the cord being fastened at the terminal of the primary brake arm to accommodate the brake cable coming in a non-longitudinally straight orientation for achieving the insertion at a certain inclination to apply the optimal brake.