Abstract: The present invention discloses an automatic idling-up controlling device of an engine including: a vehicle speed sensing member for sensing a running speed of a vehicle and producing a corresponding signal; an engine coolant temperature sensing member for sensing an engine coolant temperature and producing a corresponding signal; an engine rotation frequency sensing member for sensing a rotation frequency of an engine; a controller connected to the vehicle speed sensing member, engine coolant temperature sensing member and engine rotation frequency sensing member and producing a control signal to increase an injected quantity of a fuel, if a warming-up action is necessary, by determining a state of the engine by of an engine coolant and an engine rotation frequency when the vehicle is halted; and an actuator controlling member connected to the controller and varying by a controlling signal applied to the controller to vary a quantity of a fuel injected to an inside of a cylinder of the engine.