A valve timing adjusting device for and engine includes a sprocket configured to rotate by receiving drive power from a driving shaft, a vane rotor fixed to a driven shaft so as to be rotatable relative to the sprocket, a housing that includes an oil chamber housing the vane rotor and is fixed to one end in a thickness direction of the sprocket, a bolt fixing the sprocket to the housing, and a knock pin inserted into a sprocket hole formed in the sprocket at one end thereof and into a housing hole formed in the housing at the other end thereof to restrict relative relation between the sprocket and the housing. The knock pin abuts against an inner wall of the sprocket hole at one end thereof, and abuts against an inner wall of the housing hole at the other end thereof.