A valve timing adjustment device includes a drive-side rotating body that rotates in conjunction with a crankshaft, a driven-side rotating body that rotates integrally with a camshaft, a speed reduction mechanism that transmits rotation while allowing relative rotation between the drive-side rotating body and the driven-side rotating body. The driven-side rotating body includes a fastening portion fastened to the end portion of the camshaft by a center bolt, a bearing portion that is located radially outward of the fastening portion and that axially supports the drive-side rotating body, and a fitting outer surface that is fitted to a regulating member on a side where an outer diameter of an axial contact surface with the other member on one side and the other side in the axial direction of the driven-side rotating body is large.