A hydraulic lash adjuster comprising: a bottomed cylindrical body to be inserted into a fixing hole provided in an internal combustion engine, a bottomed cylindrical plunger slidably inserted into a cylindrical portion of the bottomed cylindrical body, a plunger cap being in contact with an upper surface of the bottomed cylindrical plunger and slidably inserted into the bottomed cylindrical body, the plunger cap including a large diameter portion slidable on the body and a small diameter portion located above the large diameter portion, and a cylindrical sleeve tightly inserted into the plunger cap, wherein oil is led to an inside of the bottomed cylindrical plunger through a body side hole provided on a side surface of the body and cap side holes communicating with the body side hole and provided on a side surface of the plunger cap, a high-pressure chamber is formed between a bottom portion of the body and a plunger bottom portion of the plunger by a check valve mechanism provided at the plunger bottom portion of the plunger, and the lash adjuster being constituted so that an even number of cap side holes are provided and all of the cap side holes are disposed in a plane perpendicular to a shaft center of the body, characterised in that the diameter of the large diameter portion of the plunger cap which slides on the body is different between a portion upper than the cap side holes and a portion lower than the cap side holes such that oil passing resistance in a portion formed on an outer circumference of the large diameter portion of the plunger cap inserted into the body and slidable in an axial direction of the body and located above the cap side holes is lower than oil passing resistance of a portion below the cap side holes, and the portion of the large diameter portion of the plunger cap located above the cap side holes is formed with an adjusting groove (28a, 28b, 29a, 29b). a bottomed cylindrical body to be inserted into a fixing hole provided in an internal combustion engine, a bottomed cylindrical plunger slidably inserted into a cylindrical portion of the bottomed cylindrical body, a plunger cap being in contact with an upper surface of the bottomed cylindrical plunger and slidably inserted into the bottomed cylindrical body, the plunger cap including a large diameter portion slidable on the body and a small diameter portion located above the large diameter portion, and a cylindrical sleeve tightly inserted into the plunger cap, wherein oil is led to an inside of the bottomed cylindrical plunger through a body side hole provided on a side surface of the body and cap side holes communicating with the body side hole and provided on a side surface of the plunger cap, a high-pressure chamber is formed between a bottom portion of the body and a plunger bottom portion of the plunger by a check valve mechanism provided at the plunger bottom portion of the plunger, and the lash adjuster being constituted so that an even number of cap side holes are provided and all of the cap side holes are disposed in a plane perpendicular to a shaft center of the body, characterised in that the diameter of the large diameter portion of the plunger cap which slides on the body is different between a portion upper than the cap side holes and a portion lower than the cap side holes such that oil passing resistance in a portion formed on an outer circumference of the large diameter portion of the plunger cap inserted into the body and slidable in an axial direction of the body and located above the cap side holes is lower than oil passing resistance of a portion below the cap side holes, and the portion of the large diameter portion of the plunger cap located above the cap side holes is formed with an adjusting groove (28a, 28b, 29a, 29b).