Disclosed is a mediator-less microbial fuel cell comprising a cathode compartment, an anode compartment, with or without glass wool and glass bead for separating the two compartments, an element for feeding air to the cathode compartment, and an element for feeding wastewater to the anode compartment. The cell further comprises an element for controlling the distance between the cathode compartment and the anode compartment. Graphite felt or graphite felt coated with a metal such as platinum is used as an electrode of the cathode compartment, and a buffer solution is used in the anode compartment. A mediator-less microbial fuel cell according to the present invention can be operated without using an expensive cation-exchange membrane, of which efficiency is by no means inferior to prior wastewater treatment methods.