A valve driving device to open or close a valve includes a cam having a cam groove, a follower movably fitted in the cam groove, and a rod having a pivot rotatably supporting the follower. The rod has a first end connected to the cam through the follower and the pivot, and a second end connected to the valve. The rod applies a load to the valve in a load applying direction corresponding to an axis direction of the rod. A center axis of the rod is perpendicular to a tangent of a contact face between which the cam and the follower are contact with each other when the valve is totally closed or opened.