PURPOSE: To obtain a gas-liquid contactor, comprising plates each functioning as an economical and efficient evaporator or absorber by separating a liquid and a heat exchanging fluid in sealing-tight manner and forming a support and a wall of a vertical stack of plates which is offset angularly with respect to one another through rotation according to the axis of the support.

CONSTITUTION: Each plate 2 in a stack 29 of three plates 2 constituting a carrier of spiral staircase has a horizontal plane 3 called tread and a vertical plane 4 called riser, wherein the plate 2 is offset angularly from each other by an angle Phi about the central axis. A stack-like trickling film 5 of the plate 2 flows on the tread 3, while being spaced apart by some distance from the riser 4 without causing any significant mixing of liquid flow over a length L1, i.e., without accompanying the so-called 'complete mixing flow', when the trickling film 5 traverses the riser 4 over a length L2. The plate 2 comprises an annular part 9 having an inside diameter Ri and an outside diameter Re, and an inner fin 10 in the form of a part of a flange having an inside diameter Rt and an outside diameter Ri.