There is provided a rocker arm of a kind in which even though the rocker arm is manufactured by the use of a press working technique the arm width can be minimized while the flat outer surface region of a required width is secured on an outer surface of the connecting wall, thereby contributing to reduction in size and weight of the rocker arm. This rocker arm is capable of being driven by a cam for selectively opening and closing a valve of an internal combustion engine. This rocker arm includes an arm body prepared by bending a single plate material to represent a generally inverted U-shaped section including opposite side walls and a connecting wall bridging between the opposite side walls. A roller engageable with the cam is rotatably mounted on a portion of the arm body generally intermediate of the length thereof. A valve drive element is mounted on one end of the arm body for driving the valve, while an end portion of the connecting wall adjacent the other end of the arm body is formed with an internally helically threaded hole for threadingly receiving therein an externally helically threaded pivot member. An outer chamfered corner delimited between an outer surface of the connecting wall and an outer surface of each of the opposite side walls and formed by bending is deformed to represent a plastically deformed portion so formed by means of a plastic deformation technique that the outer chamfered corner represents a small radius of curvature R.