A variable valve timing mechanism comprises a drive shaft including a rocker arm, a control shaft, a stopper, a first spring member and a second spring member. The rocker arm opens and closes at least one of an intake/exhaust valve in response to rotation of the drive shaft. The control shaft changes a position of the rocker arm to continuously change valve lift characteristics of the intake/exhaust valve in response to rotation of the control shaft by driving a control shaft actuator. The stopper regulates an operating range of rotation of the control shaft between upper and lower limits. The first and second spring members urge the control shaft towards the upper and lower limits, respectively. The first and second spring members return the control shaft to a balance position between the upper limit position and the lower limit position when the internal combustion engine stops.