Galvanic vestibular stimulation (GVS) induces a sensation of virtual acceleration as vestibular information and its application is expected as a wearable interface because it does not need a large device like a motion platform. In particular, GVS with alternating current (AC) can influence vision that mainly consists of a torsional component. This research aimed to quantitatively evaluate the effects of GVS on visual perception, and to infer its cause. To investigate these issues, we conducted psychophysical experiments during GVS with AC that consisted of three different image presentation methods; images fixed on spatial coordinate, head coordinate and retina coordinate systems. It is suggested that the visual motion perception induced by GVS is mediated by eye movements. As well, the stimulus frequency response of the current threshold, at which the subjects perceived visual motion, showed a U-shaped curve for stimulus frequency dependency.