A direct current (DC)-to-DC conversion apparatus is provided. The provided DC-to-DC conversion apparatus is composed of two boost circuits, in which inputs of both boost circuits are connected in parallel, and outputs of both boost circuits are connected in series. Accordingly, when the provided DC-to-DC conversion apparatus is operated, the DC input power would be firstly sampled and determined, and then the operations of the first and the second switch devices disposed therein would be controlled in response to the sampled-determined result, such that both boost circuits would be respectively operated in different input conditions, for example, the input is normally-connected or the input is reverse-connected. Accordingly, regardless of the input of normal connection or the input of reverse connection, the provided DC-to-DC conversion apparatus can perform the function of DC-to-DC conversion, thereby enabling the applied product to be normally operated even the input is reverse-connected.