An ultrasonic measurement method, including: receiving a plurality of ultrasonic waves that have been spectrum-spread with different codes by first and second wave-receivers; de-spreading the first and second receive signals respectively with a selected code and a non-selected code; obtaining an amplitude ratio between the produced selected de-spread signal and the non-selected de-spread signal; determining a threshold value based on the amplitude ratio; extracting a signal having an amplitude greater than or equal to the threshold value from the non-selected de-spread signal to thereby produce an interfering signal; spreading the interfering signal with a corresponding non-selected code and then removing the interfering signal from the first and second receive signals to thereby produce first and second receive signals from which the interfering signal has been removed; de-spreading the first and second receive signals from which the interfering signal has been removed each with the selected code to thereby obtain first and second de-spread signals from which the interfering signal has been removed; and calculating the propagation distance and the propagation direction of the selected ultrasonic wave based on points in time at which the first and second de-spread signals arrive at the first and second wave-receivers.