The invention discloses an oil-water separator, belongs to oil-water separation devices in the technical field of environment protection equipment and aims to provide an oil-water separator with a good oil-water separation effect and improve oil-water separation efficiency. The oil-water separator comprises a shell, wherein a water drainage hole is formed in the side wall of the shell; a first partition plate and a second partition plate are arranged in an inner cavity of the shell and are used for dividing the inner cavity of the shell into a primary filtering area, a water areabalancing area and an oil collection area; a flow slowing box and a water area balancer are arranged in the water areabalancing area; the flow slowing box is communicated with the bottom of the primary filtering area; an outer discharging hole is formed in the side wall of the flow slowing box; a first water inlet is formed in the bottom of the water area balancer and is communicated with the water drainage hole; an oil leaking plate is arranged above the oil collection area and is lower than the bottom of the second partition plate; an oil leaking hole is formed in the oil leaking plate; the top of the first partition plate is higher than the top of the water area balancer and the top of the second partition plate; the top of thesecondpartition plate is equal to or higher than the top of the water area balancer.