An eco-run control device is mounted on a vehicle and is capable of performing eco-run control to stop an engine when predetermined stop requirements are satisfied and restart the engine when predetermined start requirements are satisfied later. This eco-run control device includes: a monitoring unit that monitors the state of an ignition; a communicating unit that communicates with a plurality of control devices that receive power supplies from a power supply line that is connected to a power source via the ignition; and an initialization controlling unit that initializes the data with respect to the eco-run control stored in a memory, when the monitoring unit determines that the ignition is in an OFF state, and that the communications with two or more of the control devices are interrupted.