To permit the mounting of a sleeve on a heat transfer tube so as to be stabilized as well as the unifying of the heights of respective sleeves.

A falling liquid type heat exchanger is provided with a tubular main body unit, equipped with an upper header, a lower header, a first tube plate 31 positioned at the upper end of the same and a second tube plate positioned at the lower end of the same, a plurality of heat transfer tubes 33, arranged so as to be extended between the first and second tube plates, and the sleeve 43, arranged so as to be faced to the inside of the upper head and whose predetermined part is projected out of the first tube plate 31 to conduct liquid on the first tube plate 31 to flow into the heat transfer tube 33. In this case, a projected part is formed on the predetermined part so as to be projected inward in the radial direction of the same. The other part in the sleeve 43 is attached to the heat transfer tube 33 by expanding toward the heat transfer tube 33.