We have studied on the experimental variables such as optimum adsorption condition, color changes, light fastness, antimicrobial properties, and wash durability of the cotton fabrics treated with gallnut extracts. Treatment of gallnut extracts on the cotton fabrics was optimally achieved at 6$0^{circ}C$ for 60min. Gallnut extracts did not cause unintended color change after treatment on the cotton fabrics dyed with reactive dyes. The cotton fabrics treated with gallnut extracts showed good light fastness, though we took into the account the extract is a natural material. The cotton fabrics treated with 10.0% o.w.f. of gallnut extracts had strong antimicrobial activity and good wash durability.