An ESD device disposed on a substrate is provided. The ESD device includes a first well, a second well, a first poly-silicon region, a second poly-silicon region and a first protection layer. The first well has a first conductive type and is disposed on the substrate. The second well has a second conductive type, is disposed on the substrate and is adjacent to the first well. The first poly-silicon region is disposed on the first well. The second poly-silicon region is disposed on the second well. The first protection layer covers portions of the first well, the second well, the first poly-silicon region and the second poly-silicon region. There is no doping region in the portions of the first well and the second well which are covered by the first protection layer and between the first poly-silicon region and the second poly-silicon region.