PURPOSE: To enable a user to surely detect an obstacle close at user's feet with a simple constitution by mounting a distance measuring sensor for measuring the distance to the obstacle near his feet to the user's leg part.

CONSTITUTION: A pressure change is detected by a pressure sensor when the shoes land on the ground accompanying walking of the user. A landing detection signal is then outputted to a distance measurement control section 12. The sensor section 11a or 11b irradiates the ground surface with measuring waves of ultrasonic waves or IR light in nearly parallel therewith or slightly downward from a measuring wave radiation section and a measuring wave accepting section attains a photodetecting state. Further, the distance measuring sensor section 11 measures the distance to the forward obstacle by making forward scan in accordance with the moving of his legs. A distance measuring section 14 outputs a detection signal S4 to an alarm control section 16 when the measured distance is in a detection region of the obstacle. The control section 16 outputs alarm signals S5, S6 according to whether the detection signal S4 is on the right side or the left side.