A cooling apparatus is used for cooling an electronic element. The cooling apparatus includes a fan and a fan duct. The fan is for generating airflow. The fan duct including an inlet, an outlet, and a first metal net fixed in one of the inlet and the outlet, is for guiding the airflow. The inlet is for allowing air to enter the fan duct. The outlet is for allowing air to flow out from the fan duct. The first metal net defines a plurality of guiding holes for the airflow to pass through, and a maximum distance in a traverse direction of each of the guiding holes is smaller than one twentieth of a wavelength of an electromagnetic wave emitted from the electronic element. An electronic device using the cooling apparatus is also disclosed.