Disclosed is a ship bilge sewage treatment device, which belongs to the technique field of ship pollution prevention. The device comprises a strainer, a centrifugal pump, an oil-water separator, a bidirectional flow ultra-filtration membrane separation component, a heating container, a middle filter, a fine filter, a reciprocating pump, an electromagnetic flow meter, an oil element alarm monitoring recorder, a clear water tank, a chemical agent box, a control unit, a one-way valve, a two-position and two-way solenoid valve and a two-position and three-way solenoid valve. When the emulsified oil element in the bilge water is rather low, the device enables the water quality to reach the standards through mechanical separation and filtration by the filter. When the emulsified oil element contained in the bilge water is rather high, the device is added with the membrane separation component for filtration on the basis of mechanical separation, so the water quality can meet the discharge standard. Meanwhile, measures such as water preheating treatment before membrane, sewage flow control, and back flushing by clear water and chemical agent are adopted to reduce the membrane fouling, thereby ensuring the operation of sewage disposal work and extending the service life of membrane. The sewage treatment device has obvious economic benefit and social benefit.