In an ultrasonic inspection method or ultrasonic inspection system in which an ultrasonic wave is propagated to an test object via a medium such as a liquid or a gas, an incident position of the ultrasonic wave is accurately and reliably identified. In an ultrasonic inspection method based on an immersion technique, an optical irradiator is mounted on an ultrasonic wave transmitting/receiving unit, an optical marker is irradiated from the optical irradiator to the test object, and an irradiated position of the optical marker is imaged using imaging equipment in order to perform inspection.