A bone strength diagnostic device comprises oscillators, a determination index calculator, a tracking start point setting component, and a tracking execution component. A plurality of the oscillators are disposed in a line to acquire echo signals of a transmitted ultrasound beam. The determination index calculator calculates a determination index expressing a probability that the echo signal is a reflected wave from the surface of a cortical bone. The tracking start point setting component sets a tracking start point at a signal waveform timing corresponding to the echo signal for which the determination index satisfies a specific condition and that is received by one of the plurality of oscillators. The tracking execution component successively sets tracking points for the echo signals acquired from other oscillators using the tracking start point as an origin.
