A casing for a heat-dissipating fan includes an annular wall and a base. The annular wall includes an air inlet in a first end thereof and an air outlet in a second end thereof. The base is securely mounted in the air inlet of the base, with a plurality of ribs extending between the annular wall and the base. A plurality of mounting portions are provided between the annular wall and the base to allow the heat-dissipating fan to be fixed to an object. Since the mounting portions are located inside the annular wall, minimization of the casing is realized.