A high voltage device includes: a semiconductor layer, an isolation structure, a drift oxide region, a well, a body region, a body contact, a buffer region, a gate, and a source and a drain. The body contact includes a main body contact and at least one sub-body contact. The main body contact is adjacent to the source, wherein the main body contact and the source are rectangles that extend along a width direction, and the source is located between the main body contact and the gate. The sub-body contact extends from the main body contact toward the gate and contacts an inverse current channel. The buffer region encompasses all the periphery of the body region below a top surface of the semiconductor layer, wherein an impurity concentration of the buffer region is lower than an impurity concentration of the body region.