To provide an oiler which does not allow oil to leak out even at elevated temperatures during storage by covering the upper end of a main body container with a cap, and providing an internal pressure regulation means for selective communicating the inside to the outside of the main body container via a part of the cap.

A main body container 1 is filled with oil B and covered at its upper end with a cap 2, and an air vent valve 8 is provided to serve as an internal pressure regulation means for selectively communicating the inside to the outside of the main body container 1 via a part of the cap 2. The air vent valve 8 has a cylinder 9 vertically projected from the inner surface of the cap 2, and has a ball 10 enclosed in the cylinder 9, the ball 10 being held floating with a microclearance (d) between it and the interior wall of the cylinder 9 and allowed to freely move up and down inside the cylinder 9. Thus an oiler can be obtained which does not allow oil to leak even at elevated temperatures when the main body container 1 is stored.