The durability of handmade paper prepared by potassium carbonate cooking of paper multiberry (Broussonetia Kazinoki Sieb).was investigated. The potassium carbonate paper before and after heat aging had better strength properties, breaking length and folding endurance than those of the soda paper, except of lower brightness .After 30 days of heat aging , these strength properties were still maintained . however, there was almost no difference in the infrared spectra and the crystallinities calculated by X-ray diffraction curves between the potassium carbonate paper and the soda a paper. The durability of the potassium carbonate paper was though to be due to decrease in the pulp damage caused by weak alkaline cooking condition. The results indicated that the paper prepared by the potassium carbonate cooling method could have better permanence than that prepared by the conventional soda cooking method.