To provide a small-size, simply-structured, and low-cost one-pedal type pedal apparatus that is easily mountable to an existing brake pedal without modifying the brake pedal, and that does not extendthe pedal tread toward a driver side, enables a brake and an accelerator to be operated even in a state where the right foot heel is placed on a floor, and permits slight misalignment of a pedal treading position by surely being operated in an accelerator closing direction during braking. This pedal apparatus is provided with: a frame that comprises a bracket mountable to an existing brake pedal,and a base extended rightward from the bracket; an accelerator pad that is mounted so as to be slidable left and right on the base via a slide mechanism provided to the upper surface of the base; anda transmission means for transmitting the position of the accelerator pad to an automobile accelerator device. The pedal apparatus is characterized in that the base is arranged so as to incline downward toward the bracket, the accelerator pad has a shape in which a tread is lower than the tread of the brake pedal in a state where the accelerator pad is set at the leftmost position, a biasing meansfor biasing the accelerator pad leftward is provided, and the base is provided to the bracket at an angle where the right end of the base is closer to the driver side.