The microbial electrode is constructed having a substrate(3) made of an insulating material, an electric conductor(2) which is fixed on the substrate and a membrane containing microorganism cells(1) which is fixed on the conductor. The microbial sensor(20) is constructed having the microbial electrode above described and a conductor(11) to act as a counter electrode fixed on the insulating material of the surface of the substrate of the electrode which is opposite to the surface where the membrane containing microorganism cells is fixed.