A dual drum type continuous casting device capable of casting a sheet metal (4) by feeding molten metal (3) to a molten metal sump formed of a pair of cooling drums (1) rotated in the directions reverse to each other and a side dam (2) and bringing the molten metal into contact with the surface of the cooling drums (1) to cool the molten metal so as to form a solidified shell, wherein the cooling drums (1) are formed of a drum shell body (11) having a shaft part at both side end parts thereof and a drum sleeve (10) fitted onto the outer peripheral part of the drum shell body (11), and a means to avoid various types of adverse effects caused by a difference in thermal expansion between the structural members of the drum shell body (11) in the casting is provided to increase the reliability of the device and the quality of the casting.