A high voltage metal oxide semiconductor device comprising a substrate, an N-type epitaxial layer, an isolation structure, a gate dielectric layer, a gate, an N-type drain region, a P-type well, an N-type source region, a first N-type well and a buried N-doped region is provided. The first N-type well is disposed in the N-type epitaxial layer under the isolation structure and on one side of the gate. The first N-type well overlaps with the N-type drain region. The buried N-doped region is disposed in the substrate under the N-type epitaxial layer and connected to the first N-type well.