A valve operating device for an internal combustion engine is capable of increasing a negative valve overlapping duration when maximum lift amounts of an intake valve and an exhaust valve are small. The valve operating device is provided with intake-side and exhaust-side characteristic adjustment mechanisms for adjusting operating characteristics of an intake valve and an exhaust valve. Each characteristic adjustment mechanism has a control cam rotating integrally with a cam shaft, an electric motor that causes a holder pivoted on the cam shaft to rotate about the cam shaft, a sub-rocker lever pivoted on the holder and caused to oscillate by the control cam, and a valve cam that is caused to oscillate around the cam shaft by oscillation of the holder and the sub-rocker lever, for causing oscillation of main rocker levers. The electric motor causes the holder to oscillate in such a manner that the valve open timing of the intake valve is retarded as a maximum lift amount of the intake valve becomes smaller and the valve close timing of the exhaust valve is advanced as a maximum lift amount of the exhaust valve becomes smaller.