Connection structure of multi-channel tube with branching tube and connection method therefor

A connection structure of a multi-channel tube (1) with branching tubes (10) is provided with a multi-channel tube having an end, the multi-channel tube including; an outer tube (2); a partition (3) being formed in a unitary body and running parallel with the outer tube, the partition partitioning an interior of the outer tube into two or more channel holes; and a passage (6,16) formed at an end of the partition, the passage linking the channel holes; two or more branching tubes respectively inserted into the channel holes to an insertion depth greater than a depth of the passage measured from the end of the multi-channel tube; and brazing material (20) spreading beyond the passage over clearances between the multi-channel tube and the branching tubes and connecting the multi-channel tube and the branching tubes.