A reinforcement rib is provided from surroundings of a boss section continuously extending towards a lower-end portion thereof, and the boss section is provided substantially perpendicular to a flat section of the reinforcement rib; this improves the strength of the pedal arm as appropriate including the surroundings of the boss section on which a large load is applied at the time of depressing operation, and thus makes it possible to achieve reduction in weight and costs by thickness reduction while securing a required strength. Although the pedal arm is of a flat plate shape, providing a front side flange and a rear side flange allows for forming a front side recess and a rear side recess between the reinforcement rib and the respective front side flange and rear side flange.