In previous studies of human information processing, the visual separate system and the auditory separate system have been frequently studied. However, human related characteristic between visual and auditory systems has not been investigated substantially. If the mechanisms of human visual and auditory parallel information processing are elucidated, the finding will contribute to improving technical systems. In our previous studies, human related characteristic between visual search and speech perception is studied. The results showed the mutual effect between visual information processing and auditory information processing in the visual and the auditory parallel information processing. However, to clarify the cause of many car accidents lies in the use of car-phone on driving, it is necessary to use the same kind of visual and auditory stimuli in psychological experiments. In this paper, characteristic of reaction time in parallel information processing of human visual and auditory system is measured by using the same kind of stimuli. The experimental results show the factors that influence the visual and the auditory reaction time are the difficulty of the visual and the auditory stimuli and the timing of the visual and the auditory inputs. The experimental results also suggest that one of the causes of car accidents (to use car-phone while driving) is that the human visual information processing is affected by the auditory information.