An eco-run control device is provided. A control unit is configured to perform an eco-run control of stopping an engine on the basis of stop conditions and of restarting the engine on the basis of restart conditions. A starter driving unit is configured to drive a starter for restarting the engine. A test unit is configured to perform a failure test of the starter driving unit to determine whether the starter driving unit is out of order before the control unit stops the engine by the eco-run control. A nullifying unit is configured to nullify the failure test by the test unit when it is detected that a power supply voltage supplied to the starter driving unit drops below a predetermined value. A prohibiting unit is configured to prohibit the control unit from performing the eco-run control when the test unit determines that the starter driving unit is out of order. The prohibiting unit prohibits the control unit from performing the eco-run control in a case where the nullifying unit nullifies the failure test by the test unit during a test period in which the test unit performs the failure test.