An electronic control apparatus has a microcomputer including a first CPU and a second CPU configured to perform calculation processing and control processing for a vehicle control device such as a variable gear ratio steering device. The first CPU and the second CPU calculate temporary detection values of an operation amount of an actuator based on a detection signal of a sensor, respectively. The temporary detection values are compared to determine whether the vehicle control device is controllable based on the detection signal of the sensor. Thus, the electronic control apparatus is reduced in size, and calculation results are monitored each other within one microcomputer.