PURPOSE: To make on operator skillful to an operation without requiring a manual by learning an operation method and the content of an error from the outline to the details in several levels by making the operator instructable with a key operation.

CONSTITUTION: The device consists of a guidance display instruction input means 1, a message number registration means 2, a message file control means 3, a message file read means 4, a message shift means 5 and a display means 6. When the length of a display message is longer than display digits at the time of displaying an operator guidance on a small display screen, the message is successively shifted and displayed and the message is sequentially displayed from the outline to the details by setting the message in hierarchy structure. Thus, the operator does not need to refer to the manual, and the guidance can effectively be used.