As virtual environment (VE) technology has become more disseminated, harmful physiological influences on users of VE have been reported such as simulator sickness and motion sickness – collectively called VE sickness. For VE safety and comfort, we note a new dynamic visual illusion, called “rotational dynamic illusion”. Several psychophysical experiments measuring head movement in illusion observation suggest that perceptive features of rotational dynamic illusion are closely related to balance, which causes VE sickness. These features will be effective in realizing VE safety and comfort and trigger advances in VE technology development.