There is provided a support device for a rocker arm, which is capable of suppressing deformation or wear of a washer, and greatly improving the working efficiency in assembling the washer to the rocker arm. The support device supports the rocker arm having a supported portion, for driving an engine valve of an internal combustion engine. A rocker shaft is supported between a pair of shaft holders arranged in the cylinder head, for pivotally supporting the rocker arm thereon via the supported portion. A washer has engaging pieces, and is attached to one of opposed ends of the supported portion of the rocker arm and one of the shaft holders, in a manner interposed between the opposed ends. The one of the opposed ends is formed with an annular engaging portion for having the washer engaged thereon via the engaging piece.