A scavenger receptor A expression down-regulator and a drug for preventing or treating arteriosclerosis which contain, as the active ingredient, a C-terminal globular domain of adiponectin, adiponectin, or a gene encoding the domain or adiponectin.According to the present invention, there is provided a preventive or therapeutic agent capable of directly preventing intimal thickening, which constitutes an essential feature of arteriosclerosis. This effect can be attained through arresting the onset and development of arteriosclerosis by reducing the expression level of scavenger receptor A in arterial walls and preventing lipid buildup in macrophages.