An engine control device of a vehicle engine includes a processor that detects an operation state of the engine and controls an output of a heater which heats an intake air oxygen concentration sensor detecting oxygen concentration of intake air of the engine. The intake air includes a portion of exhaust gas recirculated to an intake passage of the engine as EGR gas. The processor controls the output of the heater, according to a detected operation state of the engine, so that the intake air oxygen concentration sensor enters one of (i) an active state where a temperature of the intake air oxygen concentration sensor becomes greater than or equal to an activation temperature, (ii) a semi-active state where the sensor temperature is lower than the activation temperature and higher than an inactivation temperature, and (iii) an inactive state where the sensor temperature is lower than the inactivation temperature.