An electrostatic discharge (ESD) protection device is provided. The ESD protection device includes an epitaxy layer disposed on a semiconductor substrate. An isolation pattern is disposed on the epitaxy layer to define a first active region and a second active region, which are surrounded by a first well region. A gate is disposed on the isolation pattern. A first doped region and a second doped region are disposed in the first active region and the second active region, respectively. A drain doped region is disposed in the first doped region. A source doped region and a first pick-up doped region are disposed in the second doped region. A source contact plug having an extended portion connects to the source doped region. A ratio of an area of the extended portion covering the first pick-up doped region to an area of first pick-up doped region is between zero and one.