A hydraulic lash adjuster having a reduced number of elements, yet capable of suppressing air from infusing into a high-pressure chamber. A plunger is fitted in a body. A reservoir is formed in the plunger. The plunger's head portion is formed with a communication hole for communicating its interior with its exterior. A high-pressure chamber is disposed and between the plunger and the body. An oil supply hole is formed in the peripheral wall of the plunger. A return spring is provided between the body and the plunger. A valve mechanism is provided at the plunger's bottom. Provided on the inner periphery of the plunger is an inclined area, subjected to impingement of oil jet ji and serving as an impingement area, such that the impingement area is inclined to fall in the direction of the ejected oil as the area nears the plunger's head portion.