The method for observing adipose tissue includes a step A in which a clearing reagent is applied to the adipose tissue in the body, the first refraction index of the adipose tissue is decreased by heating the adipose tissue, A step B of bringing the refractive index closer to the refractive index, and a step C of observing the inside of the adipose tissue infiltrated with the clearing reagent.脂肪組織の観察方法が、体内の脂肪組織に透明化試薬を適用する工程Aと、前記脂肪組織を加温して前記脂肪組織の第1の屈折率を下げ、前記透明化試薬の第2の屈折率に近づける工程Bと、前記透明化試薬が浸透した前記脂肪組織の内部を観察する工程Cと、を備える。