Abstract: An advection fan includes a fan frame, an impeller and a cover plate. The fan frame has a bottom plate and a lateral wall. A shaft seat is arranged on the bottom plate. The lateral wall surrounds the shaft seat and has an inner peripheral face. The lateral wall includes first and second air-guiding portions. An air inlet and an air outlet are formed between the first and second air-guiding portions. The first air-guiding portion includes a first guiding face intersecting the inner peripheral face by a first included angle, which is smaller than 180 degrees. The second air-guiding portion includes a second guiding face. A distance between the first and second guiding faces is gradually reduced from the air inlet towards the center of the fan frame. The impeller is rotatably coupled with the shaft seat. The cover plate is coupled with the lateral wall.