A chain transmission device for driving a camshaft, comprising: a driving sprocket mounted to a crankshaft; a driven sprocket mounted to a camshaft; a timing chain looped over the driving sprocket and the driven sprocket; a pivotable chain guide (A 1) provided on one side of a slack side of the timing chain, and retaining a plurality of rotatable rollers for guiding movements of the timing chain so as to be spaced from each other in a direction in which the timing chain is moved; and a chain tensioner for applying an adjustment force to a remote end of the chain guide (A 1) remote from a center of pivoting movement of the chain guide, thereby pressing the rollers against the timing chain, characterized in that: a ratio (D 1 /D 2) between a pitch circle diameter D 1 of the driving sprocket and an outer diameter D 2 of the rollers is within a range of 5/3 to 5/1, characterized in that the rollers are formed by drawing a thick metal plate having a thickness of 1 mm to 3 mm, and the rollers comprise roller bearings each comprising a shell-shaped outer race having inwardly extending flanges at both ends, a plurality of roller elements received in the outer race, and a retainer for retaining the roller elements, and the shell-shaped outer race guides movement of the timing chain, while being in rolling contact with the timing chain. a driving sprocket mounted to a crankshaft; a driven sprocket mounted to a camshaft; a timing chain looped over the driving sprocket and the driven sprocket; a pivotable chain guide (A 1) provided on one side of a slack side of the timing chain, and retaining a plurality of rotatable rollers for guiding movements of the timing chain so as to be spaced from each other in a direction in which the timing chain is moved; and a chain tensioner for applying an adjustment force to a remote end of the chain guide (A 1) remote from a center of pivoting movement of the chain guide, thereby pressing the rollers against the timing chain, characterized in that: a ratio (D 1 /D 2) between a pitch circle diameter D 1 of the driving sprocket and an outer diameter D 2 of the rollers is within a range of 5/3 to 5/1, characterized in that the rollers are formed by drawing a thick metal plate having a thickness of 1 mm to 3 mm, and the rollers comprise roller bearings each comprising a shell-shaped outer race having inwardly extending flanges at both ends, a plurality of roller elements received in the outer race, and a retainer for retaining the roller elements, and the shell-shaped outer race guides movement of the timing chain, while being in rolling contact with the timing chain. a ratio (D 1 /D 2) between a pitch circle diameter D 1 of the driving sprocket and an outer diameter D 2 of the rollers is within a range of 5/3 to 5/1, characterized in that the rollers are formed by drawing a thick metal plate having a thickness of 1 mm to 3 mm, and the rollers comprise roller bearings each comprising a shell-shaped outer race having inwardly extending flanges at both ends, a plurality of roller elements received in the outer race, and a retainer for retaining the roller elements, and the shell-shaped outer race guides movement of the timing chain, while being in rolling contact with the timing chain.