Ultrasound flaw detector, ultrasound flaw detection method, and program

An ultrasound flaw detector includes: an ultrasound probe that is provided with a plurality of transducers and that is held so that a direction in which the transducers are arrayed is parallel to a surface of the test object in a state where the plurality of transducers is located in the liquid; a hardware processor that, using the plurality of transducers, transmits an ultrasound beam in a first direction with a predetermined angle with respect to a normal direction of the surface of the test object and receives a reflected ultrasound wave reflected by the test object; and an ultrasound signal processor that specifies a flaw of the test object on the basis of a reception signal that has been generated by the hardware processor on the basis of the reflected ultrasound wave.