A housing structure of a fan includes a housing having multiple support bars supporting a seat plate with which a stator is combined. An impeller has a rotation shaft rotatably mounted in the stator. Each of the support bars has two ends respectively connected to the housing and the seat plate. The cross-section of each of the support bars has a highest point, and has an air guide face and an air facing face respectively extended from the highest point, and a bottom face connecting the air guide face and the air facing face. The air guide face of each of the support bars is formed with an inclined face, and an acute included angle is formed between the inclined face and a vertical line that is vertical to a horizontal line of a bottom face of the seat plate.