This oil-water separation device includes: a supply port (3b) for oily water; a flow passage that causes oily water (X4, X7) supplied from the supply port to flow so that a flow component in a horizontal direction is a main flow component; a floated oil recovery port (F) provided above an upper portion of the flow passage and also at a position spaced from a start end of the flow passage; and a settled oil recovery port (T) provided beneath the flow passage. According to the oil-water separation device, it is possible to separate an oil component from oily water that contains an oil component with higher viscosity.