An apparatus for measuring a methanol concentration is provided. The apparatus is located in a pipe which supplies liquid fuel to the anode of a direct liquid feed fuel cell, and may include a vertical supporting beam located in the pipe; a horizontal plate located on the supporting beam and having an upper surface with a predetermined roughness; and a sensor fixed to a side of the supporting beam, which generates an electrical signal through a transformation of the supporting beam resulting from variations in a viscosity of the liquid fuel running through the pipe.