An air cleaner box structured to facilitate the attaching and detaching operation of an air cleaner element While enhancing the support rigidity thereof. The air cleaner box includes a casing having a case body and the openable and closable case cover. The air cleaner element and the element holder to support the air cleaner element are contained in the casing. The element holder has an extended U-shape in cross section, and has end sections that are supported by the case body and the case cover respectively. The element holder pivots on the bottom face rear ends of the holder lower protrusions in an inclinable manner.