No-load valve lift correction curves of opening and closing cams are set by offsetting no-load curve sections of basic valve lift curves of the cams in such directions as to increase a clearance between the curves, and they are connected with remaining sections of the curves to provide normal valve lift curves of the cams. Cam profiles of the cams are set on the basis of such normal valve lift curves. The cam profiles are set so that an ultimate speed difference between jumping and landing speeds of a follower on an ultimate valve speed curve determined from ultimate valve lift curves, having first and second shift sections where the follower shifts from the opening cam to the closing cam and from the closing cam to the opening cam, is smaller than a basic speed difference between jumping and landing speeds on a basic valve speed curve.