To form an intra-bore cooling water passage through which the sufficient amount of cooling water can be circulated, and also secure a seal surface having sufficient width between cylinder bores even in the case that an interval between the cylinder bores located adjacently to each other is narrow.

Cylinder liners 31-33 which are located adjacently to each other, and have cylinder bores #1-#3, are brought in contact with each other by connecting parts 35, 37, 39 in which recessed parts are formed to at least one side thereof so that a liner forming body 14 having closed spaces 21, 22 among connecting parts 35, 37, 39 is formed. Molten metal is poured into a mold in which the liner forming body 14 is arranged so that a casted body having a water jacket 16 can be formed around the liner forming body 14. Holes 23, 24 through which both sides of the closed space 21, 22 and the water jacket 16 are communicated to each other, are opened to the casted body so as to form intra-bore cooling water passages 17.