A fan device includes: a fan housing configured with a receiving space defined among opposite top and bottom walls, and a surrounding side wall; a fan impeller mounted in the receiving space, disposed adjacent to an air outlet in the top wall and operable to rotate about a central axis transverse to the top and bottom walls of the fan housing; and an air-guiding unit mounted fixedly in the receiving space and disposed adjacent to an air inlet in the bottom wall. The air-guiding unit includes a central connecting member disposed axially with the central axis, and a plurality of angularly spaced apart air-guiding blades interconnecting the central connecting member and the surrounding sidewall. An angular distance between each adjacent pair of the air-guiding blades is different from that of any other adjacent pair of the air-guiding blades.