A rocker arm formed of material in a shape of sheet has a pair of side wall portions, a connection portion for a valve stem receiving portion and a connection portion for a pivot receiving portion which interconnect the side wall portions, and an open portion for arranging a roller which is formed between the two connection portions. A distance between outer side surfaces of the pair of side wall portions in the connection portion for the valve stem receiving portion is reduced in a direction from upper edges to lower edges in a step-like shape having two or more step differences, whereby a first outer side surface and a second outer side surface are formed.