Provided is a control method for controlling a SIBO buck-boost converter including a first switch coupled between an input and a first node, a second switch coupled between the first node and GROUND, a third switch coupled between a second node and GROUND, a fourth switch coupled between the second node and a first output node for outputting the positive output, a fifth switch coupled between the first node and a second output node for outputting the negative output, and an inductor coupled between the first node and the second node. The first and the third switches are turned on to energize the inductor. The first and the fourth switches are turned on to generate a positive output. The third and the fifth switches are turned on to generate a negative output.