The present invention provides a differential varactor device including a substrate having a first conductive type, a well having a second conductive type, five doped regions having the second conductive type, a first gate, a second gate, a third gate, and a fourth gate. The well is disposed in the substrate, and the doped regions are disposed in the well and arranged along a direction. The first gate, the second gate, the third gate and the fourth gate are respectively disposed on the well between any two of the adjacent doped regions, and are arranged sequentially along the direction.