Enhancement of generation of high-temperature steam using a novel adsorption heat pump is investigated. In this study, enhancement of the preheating process by the use of thermal energy storage material was investigated. The effect of the heat capacity of adsorbent on the mass of steam generated was theoretically investigated. As a result, while the mass of water vapor adsorbed during the preheating was increased with the heat capacity of the adsorbent, the temperature after the preheating process decreased. It was found that there was the maximum value in the mass of steam generated. In the experiment, an additive was inserted as the thermal energy storage material to increase the heat capacity of adsorbent. When the overall heat capacity of the packed bed of the adsorbent was increased by 18% by using the additive, the mass of steam generated per unit mass of the adsorbent was increased by 25%.