Disclosed is a ship fuel oil switching system for switching a type of fuel oil, which has been used as fuel for an engine, to another type of fuel oil as fuel for the engine. The ship fuel oil switching system comprises: a supply portion for supplying fuel oil; a circulation portion for receiving fuel oil from the supply portion and circulating the same; and a control portion for controlling the supply portion and the circulation portion. The supply portion comprises multiple tanks for storing different types of fuel oil. The engine receives fuel oil from the circulation portion. Fuel oil that remains after being used by the engine is recirculated through the circulation portion. The control portion controls the flow rate of fuel oil discharged from each of the multiple tanks, thereby adjusting the mixing ratio of fuel oil sent to the engine.