Constitute a molecular recognition probe comprising: an electrochemically active group; an activity suppression group that suppresses an electrochemical activity of the electrochemically active group; a receptor area where a molecule of a target substance is specifically recognized; and a molecule area where a steric structure is changed as a result of molecular recognition; wherein the electrochemically active group is suppressed of its activity by the activity suppression group before the molecule is recognized and restores its activity after the molecule is recognized; or constitute a molecular recognition sensor by providing an anchor area on the molecular recognition probe and fixing it on a surface of an electrode.