A biosensor measuring an analyte contained in a sample includes a lower insulating substrate (100) having at least one electrode (111-113) and an enzyme reactant layer (120) which is formed on the electrode to react with the analyte; a spacer (600) which is attached to the lower substrate and an upper substrate and is provided to form a sample injection area (610) to guide the sample to the electrode through the enzyme reactant layer; and an upper insulating substrate (700) which faces the lower substrate and has an air discharge area (710) to discharge air which is absorbed together with the sample through the sample injection area, where the air discharge area is formed on a layer different from that of the sample injection area.
