The present invention provides an adsorbent for adsorption heat pump and humidity-control air conditioner, which is capable of adsorbing an adsorbate therein and desorbing the adsorbate therefrom in a narrow relative vapor pressure range, and can be regenerated (desorption) at a low temperature. Also, the present invention provides an adsorption heat pump and humidity-control air conditioner using the adsorbent which can be effectively operated even by a low-temperature heat source, as well as methods of operating the adsorption heat pump and humidity-control air conditioner by effectively utilizing low-temperature exhaust heat. The absorbent of the present invention comprises zeolite containing (i) aluminum, (ii) phosphorus and (iii) iron and/or gallium in a skeletal structure thereof, which is substantially free from change in structure upon subjecting the adsorbent to adsorption and desorption of water vapor.