The engine control apparatus includes a computing section which performs computation for engine control in synchronization with rotation of an engine, and an A/D converter which A/D-converts an analog signal necessary for the computing section to perform the computation, the analog signal being outputted from an external device such as a knock sensor. The computing section and the A/D converter are configured to enable detection of garble in the data transmitted from the A/D converter to the computing section on the side of the computing section without affecting the operation of the A/D converter.