The present invention provides a high voltage transistor including a substrate, a first base region having a first conductivity type, and a first doped region, a second doped region, a second base region and a third doped region having a second conductivity type complementary to the first conductivity type. The first base region, the second doped region, the second base region and the third doped region are disposed in the substrate, and the first doped region is disposed in the substrate. The third doped region, the second base region and the second doped region are stacked sequentially, and the doping concentrations of the third doped region, the second base region and the second doped region gradually increase.