The performance of steam generators to generate high-temperature steam using waste heat from industrial processes was investigated. Two types of steam generators were constructed. One is a bench-scale cylindrical generator having similar structure to the laboratory-scale reactor used in the authors previous research. The other is a scaled-up generator whose flow passage area is extended to store a large amount of adsorbent for further scale-up on practical application. Temperature measurements in the bench-scale generator in the atmospheric steam generation process showed that a high-temperature region is formed above the water level due to adsorption of water vapor, while a low-temperature region below saturation temperature is formed below the water level. The mass of steam generated per unit mass of adsorbent increased with increasing energy supplied from the regeneration air and approached an asymptotic value depending on the temperature of the regeneration air. The mass of steam generated per unit mass of adsorbent increased with decreasing heat capacity of the generator.