Abstract: An automatic analysis device has a light scattering photometer incorporated therein, and improved accuracy resulting from reducing the influences from external light. The automatic analysis device includes a scattered light measurement unit disposed inside the main-body casing, and openable/closable protective covers to cover the top face of the main-body casing. A first protective cover at the center includes a light-shielding part to block external light. The protective covers include see-through parts enabling viewing of the inside. The light-shielding part is configured to cover an area of the reaction disk at least corresponding to the area above the scattered light measurement unit, thus reducing external light leaking into the scattered light measurement unit, and thus removing influences from external light on the scattered light measurement. The protective cover may have a divided structure.