Provided is a testing method for determining an oral indicator by which an oral indicator can be determined. The testing method for determining an oral indicator includes an image acquisition step of acquiring an ultrasonic image of an inside of an attached gingiva of a subject, using a measurement probe, an average brightness acquisition step of acquiring average brightness of the ultrasonic image, and an indicator determination step of determining an oral indicator of the subject by referring to the average brightness and a reference of an oral indicator.