The biosensors of the present invention comprise an electrically insulating substrate, an electrically insulating cover connected to the substrate via a spacer layer, a reaction-detecting section formed on the substrate at a region sandwiched between the substrate and cover, and comprising at least one set of electrodes, and an external terminal to be connected to the reaction-detecting section, and a sealed sample-feeding path defined between the substrate and cover by the spacer layer, where the sample-feeding path has a portion intersecting the electrodes, as well as a
cutting plane line provided at an outermost surface of the substrate or cover, which is a boundary between a sensor portion comprising electrodes and a sealed cap portion which does not comprise electrodes, and the
cutting plane line is present at a position where, when the sealed cap portion is
cut along the
cutting plane line, the
cut surface does not cross the electrodes and does cross the sample-feeding path, so that a sample-inlet port and an air-
discharge port leading from the sample-feeding path are exposed through the
cut surface. In addition, the biosensors for simultaneously measuring multiple items of the present invention comprise: a substrate; a cover connected to the substrate via a spacer layer; and a number of
biosensor units comprising substrates each containing at least one
biosensor unit which comprises a reaction-detecting section including one
electrode system and one
reagent layer on the substrate, and a sample-feeding path including the
reagent layer, wherein each of the
biosensor units comprise one
reagent layer on one sample-feeding path, a cutting plane line for dividing each of the biosensor unit-comprising substrates is provided at a top surface of the substrate or cover, the cutting plane line and sample-feeding path are placed such that, when the substrate or cover is cut along the cutting plane line, a sample-inlet port for supplying a sample solution is open to a cut surface of each biosensor unit-comprising substrate as a cut port of the sample-feeding path.