A method of measuring the thickness of a biological tissue by ultrasounds and a device carrying out such method. The method is implemented with an ultrasound probe that emits ultrasonic pulses within a body under examination and receives echoes generated from structures of the body under examination. The probe includes an array of two or more electro-acoustic transducers and, in combination, means for processing the reception signals and means for orienting one or more lines of sight, along which the emission of the pulses and/or the reception of the echoes is focused, according to different angles with respect to an axis perpendicular to the emitting surface of the probe. The thickness of the biological tissue is calculated by the time interval between the reception of the first echo and the reception of the second echo, which are relevant to the same ultrasonic pulse emitted along at least a line of sight oriented along an axis perpendicular to the surface of the biological tissue, which is defined by the iteration of measurements with the line of sight oriented at different angles and with comparisons between the measured intensity values, the orientation corresponding to the axis perpendicular to the surface of the biological tissue being the one showing the maximum intensity of the first echo.