To provide an oil-feeding opening structure for a small surface boat for preventing a damage to the oil-feeding opening or a deck, and thus preventing occurrence of a damage to a chain.

The oil-feeding opening structure has a fuel tank 13 arranged in a boat body 11, a hose 81 for fuel supply extended from the fuel tank 13 and connected to an oil-feeding opening member 82 provided above the deck 20. One end of a chain 83 is connected to the inside of the oil-feeding opening member 82. The other end of the chain 83 is connected to an oil-feeding cap 84 such that the oil-feeding cap 84 seals an oil-feeding opening 85 of the oil-feeding member 82. A protective tube 86 is provided on a portion of the chain 83 where the tube 86 comes into contact with the oil-feeding opening 85, when the oil-feeding cap 84 is removed. The oil-feeding structure prevents the damage to the oil-feeding opening or the deck, and further prevents the damage to the chain itself. As a result, oil-feeding can be operated without considering the oil-feeding opening or the deck, thereby improving the operability of the oil-feeding operation.