A control apparatus of an engine including a cylinder into which a piston is reciprocatably fitted is provided. The apparatus includes a fuel injector, a water injector, and a controller. The controller includes an engine load determining module for receiving a parameter and determining whether an engine operating range is within a low high load range or a high load range. Within the low load range, the controller controls the fuel injector to inject fuel into a center region of a combustion chamber. Within the high load range, the controller controls the fuel injector to inject the fuel in a period between a latter half of compression stroke and an early half of expansion stroke, and the water injector to inject supercritical water or subcritical water toward a crown surface of the piston in a period that is after the injection and before a mixture gas ignition.