Foldable filing cabinet

A filing cabinet includes a housing foldable to a compact folding structure, two side members engaged onto two side walls of the housing and each having a hanger rail, and one or more hanger files each having a hanging member attached to each of two lateral edges of the hanger file for engaging with the hanger rails of the side members and for supporting and suspending the hanger file on the hanger rails of the side members of the housing. Four corner members may be engaged onto the corner areas of the housing for reinforcing the housing. The filing cabinet may be easily and quickly assembled by the users themselves for suspending hanger files in the outdoors.