In a high-temperature regenerator which has vertical liquid pipe groups in the proximity of which a combustion flame and combustion gas from a burner pass and a double can wall which communicates with upper and lower portions of liquid pipes forming the vertical liquid pipe groups and is arranged at a position of a furnace wall and which heats and concentrates a diluted absorption solution passing through the vertical liquid pipe groups and the double can wall, a solution inlet for sprinkling the diluted absorption solution in an open state is provided above liquid pipes arranged on a side opposite to the burner. Since the sprinkled diluted absorption solution collects the heat of an exhaust gas while it falls to increase its temperature, when it flows into the other liquid pipes, it boils immediately and its circulation flow is activated by boiling. Therefore, total heat transfer coefficient can be increased, a local rise in the temperature of the liquid pipe groups and the can wall can be avoided, and such inconvenience as a corrosion accident and the crystallization of a solution caused by this rise in temperature can be prevented.