The present invention relates to a method for preparing an Allium ampeloprasum L. extract and a composition for preventing or alleviating obesity comprising the extract. The method comprises the steps of: obtaining homogenized Allium ampeloprasum L.; and obtaining an Allium ampeloprasum L. extract by mixing the homogenized Allium ampeloprasum L. and a solvent in a weight ratio of 1:1.COPYRIGHT KIPO 2019본 발명은 웅녀마늘 추출물의 제조방법 및 이를 포함하는 비만 예방 또는 개선용 조성물에 관한 것이다.