There are provided a measuring device for a biosensor, capable of performing a simple, accurate and short-time measurement of a specific substance in a sample without being affected by physical properties of a sample, and a measuring method. In the measuring device for a biosensor in accordance with the present invention, a biosensor is used which includes: a sample supply port; an electrode system having a measurement electrode and a counter electrode; and a portion where a sample can be irradiated with light in at least part of a sample supply pathway, to detect electrical and optical variations in the sample and determine a physical factor of the sample, so that a measurement value can be corrected.