The effect of alkali treatment on the changes in characteristics, mechanical properties, and hand of polyester fabrics was studied. Two kinds of fabrics having different yarn deniers were treated varying weight loss. The results were as follows; 1. Changes in constructional characteristics by alkali treatment were: a decrease in weight & thickness of fabric, a decrease in yarn denier, a decrease in apparent density of fabric, an increase in porosity to air, and a change fiber surface. 2. As for the changes in mechanical properties by alkali treatment, findings were : an increase in WT, RT, MIU, LC, and WC, a decrease in LT, B,2HB, G,2HG,2HGS, MMD, SMD, and RC, ana an increase in drape. 3. Changes in hand by alkali treatment were: a decrease in KOSHI and HARE, an increase in FUUURAMI, SHARI, KISHIMI, and SHENAYAUASA, and an increase in T.H.V 4. In the case of the same weight loss, the hand of 40/24 fabric being composed of thinner yarns was better than the hand of 50/24 fabric. 5. When 50/24 fabric was treated to have the same weight with 40/24 fabric, so the yam deniers of two fabrics were the same, the hand of 50/24 fabric having larger weight loss was better than the hand of 40/24 fabric.