A rocker arm formed by pressing includes: a rocker arm body substantially U-shaped in section which is made of a plate material; and a roller rotatably supported between the side walls of the rocker arm body substantially at the middle, the rocker arm body having a semi-spherical pivot engaging portion at one end, and a valve engaging portion at the other end. In the rocker arm, each of the side walls has a pivot-side portion beside said pivot engaging portion which is smaller in wall thickness than the remaining.