The present invention is related to an extract of Cucurbitaceae family plant or the purified extract isolated therefrom having anti-adipogenic and anti-obesity activity, and a composition comprising the same. The extract of Cucurbitaceae family plant of the present invention showed potent reducing activity of body weight, decreasing effect on the blood triglyceride and cholesterol level, activating activity of PPAR .alpha. and .delta., reducing activity of the gene expression of stearoyl-CoA desaturase, and preventing activity from the adipogenesis of precursor fat cells with no toxicity, therefore, those extract can be useful in treating or preventing obesity and adipogenesis-involved diseases as a medicine or health care food.