To develop an adsorbent for an adsorption heat pump (AHP), active carbons were produced by means of low-temperature KOH chemical activation using polyethylene terephthalate (PET), which has attracted attention as a material for recycling. Water vapor adsorption isotherms were measured on activated carbons formed at KOH/raw material ratio (R) of 0.8-4, and activation temperature (T-a) of 673-873 K. From the result, it was found that the best of activated carbons have about 1.7 times the amount of water vapor absorbed as that of silica gel in the AHP operation range (phi : 0.1-0.35). Moreover, it became clear that R = 3.2 and T-a = 773 K were the optimum value in present experiment range. Also, yields of activated carbons were larger than that of decomposition product. These results show the potential for production of activated carbon for AHP by this method.