This report describes the results of the basic experiment on ultrasonic method of localization of mobile robots working in very strong radiation environments in nuclear facilities or in a room filled with opaque medium such as dense smoke where video cameras cannot function. The basic characteristics of the ultrasonic sensors used, the outline of the system for sensor signal processing and the parallel processing method for structured programs are also described. The results of the experiment show that it is possible to identify the location with sufficient accuracy by proper use of the ultrasonic sensors and of signal processing method. It is also shown that countermeasures must be taken to organize a precise and stable measurement system. The parallel processing method applied in this experiment is effective on which uses synchronization for communication among multiple structured processes and can also be applied to other sensor signal processing systems. (author).