A control device of a control valve used for an intake air-gas system of an engine, the device comprising: the control valve (18, 24) which is an intake air throttle valve provided in the intake air-gas system of the engine to control the flow rate of intake air to the engine, or an EGR valve provided in the intake air-gas system of the engine to control the flow rate of EGR gas to the engine; and a control unit which determines a target opening of the control valve (18, 24) in response to the operation conditions of the engine, and controls the opening of the control valve so that the opening conforms with the target opening, wherein the control unit is configured so that in a case, where the target opening is maintained at a same level over a fixed duration, it changes the target opening, in time, from the target opening, which is determined in response to the operation conditions of the engine, and controls the opening of the control valve to confirm the tracking performance of the actual opening of the control valve in response to the change in the target opening by measuring the actual opening of the control valve, wherein the control unit changes the target opening, in time, in a range of a dead zone where the flow rate of the intake air or the flow rate of the EGR gas is not influenced by the opening of the control valve used for the intake air-gas system even when the opening of the control valve is changed, and wherein the control unit forcefully fixes the target opening at a constant level in a range within the dead zone in a case, where the target opening is not maintained at a same opening level over the fixed duration and the target opening is in the range within the dead zone. the control valve (18, 24) which is an intake air throttle valve provided in the intake air-gas system of the engine to control the flow rate of intake air to the engine, or an EGR valve provided in the intake air-gas system of the engine to control the flow rate of EGR gas to the engine; and an intake air throttle valve provided in the intake air-gas system of the engine to control the flow rate of intake air to the engine, or an EGR valve provided in the intake air-gas system of the engine to control the flow rate of EGR gas to the engine; and a control unit which determines a target opening of the control valve (18, 24) in response to the operation conditions of the engine, and controls the opening of the control valve so that the opening conforms with the target opening, wherein the control unit is configured so that in a case, where the target opening is maintained at a same level over a fixed duration, it changes the target opening, in time, from the target opening, which is determined in response to the operation conditions of the engine, and controls the opening of the control valve to confirm the tracking performance of the actual opening of the control valve in response to the change in the target opening by measuring the actual opening of the control valve, wherein the control unit changes the target opening, in time, in a range of a dead zone where the flow rate of the intake air or the flow rate of the EGR gas is not influenced by the opening of the control valve used for the intake air-gas system even when the opening of the control valve is changed, and wherein the control unit forcefully fixes the target opening at a constant level in a range within the dead zone in a case, where the target opening is not maintained at a same opening level over the fixed duration and the target opening is in the range within the dead zone.