Abstract: An adsorption heat pump includes a working fluid, an adsorption-desorption unit, and an evaporation-condensation unit connected with the adsorption-desorption unit. The adsorption-desorption unit adsorbs and desorbs vapor resulting from the working fluid, and includes an adsorbent being a porous substance. The porous substance has pores, and exhibits a pore diameter distribution curve having a maximum peak falling in a pore diameter range of from 1 to 10 nm. The pores in the diameter range of .+-.40% of pore diameter at the maximum peak have pore volume not less than 60% of a whole volume of the porous substance. The evaporation-condensation unit evaporates and condenses the working fluid. The adsorption heat pump can be operated by a low-temperature heat source, and can exhibit a large pumping temperature difference regardless of its small size.