Abstract: After a reverse bias is applied between a working electrode and a counter electrode or a reference electrode, a forward bias higher than a forward measurement bias is applied between the working electrode and the counter electrode or the reference electrode, before the forward measurement bias is applied. This reduces the time period before which an actual measuring operation is possible. When the bias is applied between the working electrode and the counter electrode or reference electrode, the bias is gradually increased in absolute value according to a predetermined time constant. This reduces damage to the membrane or membranes fixed on a surface of the electrode unit.

Abstract: The present invention provides a biosensor which is arranged to generate an electric signal corresponding to an object to be measured. The biosensor is provided with a foundation electrode which is comprised of a working electrode, a reference electrode and a counter electrode, and on the surface of which is placed an enzyme film fixed with physiologically active material, so that an electric signal corresponding to the object to be measured is generated in the foundation electrode on the basis of the result of the enzyme reaction.