Abstract: This invention provides a method for detecting an analyte, which, in specific detection of an analyte using photocurrent that is generated by photoexcitation of a sensitizing dye, can significantly simplify the structure and a detection procedure of a sensor unit and a device using the sensor unit and can realize detection with high accuracy, and also provides a sensor unit and a device using the sensor unit. According to the method, an analyte-containing sample solution and a sensitizing dye are brought into contact with the surface of a working electrode to immobilize the sensitizing dye onto the working electrode through specific binding. Subsequently, an electrolyte is supplied in situ while allowing the sample solution to be held without being removed to bring the working electrode and a counter electrode into contact with the electrolyte.