An electronic control apparatus as one of nodes connected to a communication line includes a microcomputer, a power integrated circuit for controlling power supply to the microcomputer, and a timer adjuster. The power integrated circuit has a timer for measuring a time period during which no data flows through a communication line. The timer is reset, when no data flows through the communication line and then data flows through the communication line. The power integrated circuit starts power supply to the microcomputer, when data flows through the communication line. The power integrated circuit stops the power supply when the timer reaches a threshold value. The timer adjuster prevents the timer from reaching the threshold value until the microcomputer completes a shutdown process.