An oil injection apparatus includes: a storage unit extruding lubricating oil through an ejection hole formed at a lower end thereof; a discharge unit communicating with the storage through the ejection hole and discharging the lubricating oil outside according to a pumping operation; a plurality of discharge pumps arranged at regular intervals in a circumferential direction of the discharge unit and having respective first ends disposed in the discharge unit; and a driving unit rotating in a direction to sequentially press the first ends of the discharge pumps, which are disposed in the discharge unit, thereby causing the discharge pumps to perform the pumping operation in turn.