FIG. 1 is a perspective view of a disassembled biosensor according to a preferred embodiment of the present invention. [0040] In the biosensor shown in FIG. 1, an electrode system including a working electrode 2 and a counter electrode 3 is formed by sputtering using palladium and subsequent laser trimming on the left side of an insulating base plate 1 made Of insulating resin such as polyethylene