To resolve the problem of a conventional tube for heart exchange such as that the bad brazing of a gap between a recess made by projection and a header tank insertion hole, since this projection is positioned in the insertion hole of a header tank, at manufacture of a heat exchange, in a flat tube for heat exchange which is provided with projections directed inward.

The gap between a recess and a header tank insertion hole is brought into a proper value, by regulating the depth of the recess made by projection to a certain value, whereby the bad brazing between the flat tube and the header tank is removed.