In a fuel filter module for introducing fuel from a fuel inlet into a casing and for removing foreign matter from the fuel by passing the fuel through a fuel member and for discharging the fuel through a fuel outlet to the outside of the casing, and the casing is formed to have a D-shaped cross section. With this construction, the outer diameter of the casing is not increased even when an accessory is assembled on the outside plane wall of the D-shaped casing. The casing accommodates a filter member of C-shaped cross section. The center of a C-shaped sealing member provided for sealing the upper edge of the filter member is offset from the center of the casing. By thus offsetting, sufficient areas for fuel inlet and outlet can be ensured without increasing the size of the casing.