Provided are a pharmaceutical composition for preventing or treating muscle atrophy or sarcopenia including glucagon-like peptide-1 (GLP-1), a GLP-1 fragment, a GLP-1 secretion enhancer, a GLP-1 degradation inhibitor, a GLP-1 receptor (GLP-1R) agonist, or exendin-4, and a method of treating muscle atrophy or sarcopenia by using the pharmaceutical composition. When the pharmaceutical composition for preventing or treating muscle atrophy or sarcopenia provided in the present invention is administered to a subject having sarcopenia or muscle atrophy, reduced body weight, skeletal muscle mass, and grip strength, which are caused by sarcopenia or muscle atrophy, and expression levels of genes involved in muscle production may be restored to normal states, and therefore, the composition may be widely applied to the development of effective therapeutic agents for sarcopenia or muscle atrophy.
