Abstract: An oil separator element is housed in a casing of an oil separator and consists of alternatively aligned perforated plates and plate type filter members. Adjacent perforated plates are respectively formed with perforated sections which are located opposite to each other relative to an imaginery vertical plane containing a casing longitudinal axis. A space between neighboring perforated plate and filter member is larger on the downstream side than that on the upstream side. Additionally, each filter member is formed of a three dimensional porous material having an inner structure by which oil mist can effectively coalesce.