An actual slip amount (S) of a torque converter is calculated by subtracting an actual input shaft rotational speed (Nr) of an automatic transmission from an engine rotational speed (Ne), which is the rotational speed of a crankshaft. Then, an engine rotational speed for display (Nd) is calculated by adding a slip amount adjusted for display (Sp), which is obtained by applying a predetermined correction process to the actual slip amount (S) to the actual input shaft rotational speed (Nr). The above described correction process may be a first-order-lag filter processing, for example. Thus, even when the actual slip amount (S) temporarily increases or decreases, a temporary increase or decrease in the engine rotational speed for display (Nd) may be suppressed. In other words, fluctuation or variation in the engine rotational speed for display (Nd) is suppressed. Further, Further, it is possible to provide the driver with a visually excellent direct-feeling display of engine speed Nd without impairing the drivability.