A variable valve operating device is provided that allows an ideal valve timing-lift characteristic to be realized by associating a change in a valve timing with a change in a valve lift amount. A rotation motion of a drive cam is transmitted to a slide surface of a swing member via an intermediate member. Positions of the intermediate member on the slide surface are varied in association with the rotation of a control shaft by an interlock mechanism. The slide surface is formed to be curved toward the drive cam so that the distance from the center of a camshaft increases toward the farthest point from the swing center of the swing member within the area which the intermediate member contacts from the nearest point from the swing center of the swing member within the area which the intermediate member contacts.