Abstract: An object of the present invention is to provide a cylinder liner for insert casting that can improve the joining strength between a cylinder liner and a cylinder block by reducing voids generated between the cylinder liner and the cylinder block. The above-described problem can be solved when the molten metal running index YI defined by the following Formula (1) is from 2.2 to 14.5. Molten metal running index YI=[area ratio St (%) of top portions of protrusions×molten metal infiltration volume V (mm3)/surface area A (mm2) of cylinder liner base]/average surface-to-surface distance Pav between top portions of protrusions (mm)??(1).