PURPOSE: To enable to display the inspection instructions of engine oil and air filter by suitably judging the fact that the operating state of a vehicle reaches inspection period of engine oil exchange, air filter cleaning, etc. from the total running distance and total operating time of the vehicle.

CONSTITUTION: A ROM 6 for storing a maintenance monitor program is provided in a vehicle microcomputer. Further, the set values of total running distance P1, period P2 and actual operating time P3 for oil exchange period, and total running distance P4, and period P5 for filter cleaning are stored in predetermined addresses of a non-volatile memory RAM 8 as data for indicating initial inspection time. When a key switch 11 is now closed, a CPU receives outputs α, β, and γ from the running distance meter 14, ammeter 13, and actual ammeter 12, respectively to therby judge whether they reach the set values P1 to P3. When the CPU judges that any output reaches the set value, the latter is displayed through I/O circuit 9 in a dispaly circuit 15. The filtr cleaning time is similarly judged and processed to the above.