A protection device including a substrate, a first doped region, a first well region, a second doped region, a third doped region, a fourth doped region, a second well region, a fifth doped region, and a sixth doped region is provided. The substrate, the first well region, and the third and the fifth doped regions have a first conductivity type. The first doped and the second well regions are disposed in the substrate. The first, second, fourth, and sixth doped regions and the second well region have a second conductivity type. The first well and the second doped regions are disposed in the first doped region. The second doped region is not in contact with the first well region. The third and fourth doped regions are disposed in the first well region. The fifth and sixth doped regions are disposed in the second well region.