PURPOSE: To obtain a detergent composition for eliminating labor of washing twice, having high transparency of drain in rinsing, slight dust from dried feather after washing, having excellent defatting power and cleanaibility, comprising a specific alkylene oxide derivative.

CONSTITUTION: The composition comprises (A) preferably 0.05-5wt.% (based on feather) of an alkylene oxide derivative of an aliphatic alcohol having ≥100 mg KOH/g hydroxyl number and/or an alkylene oxide derivative of a fatty acid (ester) having ≥100mg KOH/g saponification value and preferably (B) 0.5-7wt.% of a surfactant such as nonionic surfactant.