In recent years, there is a report that the traffic accident, which caused at the time of automobile operation, is increasing with the spread of mobile phones. This is considered because the cautions to operation are obstructed by use of a mobile phone. On the other hand, a driver measures the vision range which can distribute cautions at the time of operation, and it is very important to consider quantitatively the influence on which it is exerted by auditory information for the field of safety. Then, in this research, we studied how does the load in auditory information affect the vision information considered that cognitive processing levels differ, and offered the fundamental data for this field. From the result, it was shown that reaction time increases with the load of hearing information increased. Moreover, it was shown that reaction time increases more by complicating vision search. Therefore, it became clear that use of a mobile phone affects automobile operation.