We examined a new method for producing a metallic thin rod or band in which a long microchannel ran through its entire length. A tin wire and about 140 copper wires were inserted in a nickel sheath. They were cold rolled to produce a band specimen. It was heated to 1173 K and then furnace-cooled. The band specimens before and after the heat treatment were cast-in inserted in aluminum. In either case, an open microchannel formed at the site initially occupied by the tin wire, and thus the aluminum casting containing the band had the long microchannel in its body.