The present invention relates to an electric power steering apparatus. The electric power steering apparatus includes: a rack housing including a sliding recess that is formed between a motor coupling hole in which a motor pulley is mounted and a ball nut coupling hole in which a nut pulley is mounted, the sliding recess being formed to extend in a direction perpendicular to a longitudinal direction where a belt is mounted; and a tension adjusting member including a central shaft one end of which is inserted into the sliding recess, a connection member coupled to another end of the central shaft, a pair of rollers coupled to opposite ends of the connection member to tighten opposite sides of an outer peripheral face of the belt, the central shaft being slid along the sliding recess to adjust the tension of the belt.