A fully automatic ultrasonic scanner and a scan detection method is provided. The fully automatic ultrasonic scanner comprises: an ultrasonic probe (4); a driving system (5) for driving the ultrasonic probe (4) to move; and a flexible structure on which the ultrasonic probe (4) is mounted, wherein the flexible structure enables the ultrasonic probe (4) to be always along a curve of a skin surface and keep perpendicular to the skin surface during scanning. The flexible structure of the fully automatic ultrasonic scanner has self-adaptive effect, can adjust the scan trace and the probe angle in real time according to different curves of the human body, and ensure that the ultrasonic probe (4) scans against the skin surface and keeps perpendicular to the skin surface, which improves the quality of the scanned images, so as to enhance the detection rate and accuracy rate of early screening, and reduces the probability of missed diagnosis.