A direct current-direct current converter is provided. In the direct current-direct current converter, a switched capacitor converter is cascaded with at least one switch converter. In view of the feature that the switched capacitor converter includes multiple switch groups, the switch converter is configured to share at least one of the switch groups of the switched capacitor converter, which can effectively reduce the number of circuit components and increase utilization of the circuit components. In addition, the sharing of the switch group brings no negative effect on the operation of the switched capacitor converter, thus the DC-DC converter achieves an adjustable smoothing output voltage and an adjustable gain.