An electrostatic discharge (ESD) protection device including the following components is provided. A first transistor includes a first gate, a first N-type source region, and an N-type drain region. A second transistor includes a second gate, a second N-type source region, and the N-type drain region. The N-type drain region is located between the first gate and the second gate. An N-type drift region is located in a P-type substrate between the first gate and the second gate and is located directly below a portion of the first gate and directly below a portion of the second gate. The N-type drain region is located in the N-type drift region. A P-type barrier region is located in the P-type substrate below the N-type drift region. The P-type barrier region has an overlapping portion overlapping the N-type drift region. There is at least one first opening in the overlapping portion.