A boost control apparatus is provided with: a controlling device configured (i) to perform first duty control by a first control parameter if output current that flows through a reactor is not near zero, and (ii) to perform second duty control by a second control parameter if the output current is near zero, during one-side element control for driving only one of a first switching element and a second switching element, each of which is connected to a reactor in series. A rate calculating device is provided that is configured to calculate a change rate of the output current to a change amount of a duty value in the first duty control and the second duty control. A control determining device is also provided that is configured to control the controlling device to perform the second duty control regardless of the output current, if the change rate is less than a predetermined value.