PURPOSE: To easily recognize a present position by always displaying present hierarchy information on a screen in the system provided with a hierarchical structure.

CONSTITUTION: A hierarchical position is moved by a hierarchical position movement control part 5, and movement information is recorded in a hierarchy information storage part 8 and displayed on a display 1 by a hierarchy information display control part 6. Since the present hierarchy information is always displayed on the screen and further the hierarchical position can be moved by designating the information, even in the system provided with a complicated structure, the present hierarchical position can be confirmed at all times and the hierarchy can be moved without any complicated procedure.