To provide an oil pan in which the assembling facility and the sealability are more improved and improvement in durability is made possible, and to provide a method of manufacturing a gasket for an oil pan.

The oil pan 2 mounted to close an opening end of a cylinder block, includes an oil pan main body 4 having an annular flange 4A which counters an annular edge portion forming the opening end, and the annular gasket 5 of rubber material which is arranged between the oil pan main body 4 and the annular edge portion. An unvulcanized gasket material 5' is formed to have a shape, as viewed from above, substantially the same as the annular flange portion 4A and is mounted on the annular flange portion 4A. The gasket material 5' is interposed between a forming die 6 and the annular flange portion 4A so as to be molded in a predetermined cross-sectional shape and vulcanized, thereby obtaining the gasket 5 integrally united with the annular flange portion 4A. The unvulcanized gasket material 5' is an extrusion-molded rod-like material of unvulcanized rubber with a wire core 7 contained therein.