1. An ultrasonic living body tissue characterization method wherein an ultrasonic wave pulse is transmitted by a measuring system into a living body, the reflected signals are received by the measuring system and a living body tissue characteristic is measured by analysing said received signals, said method comprising the steps of: (a) analyzing the frequency of signals reflected from the region to be measured to obtain the power spectrum of said reflected signals, Er(f); (b) obtaining the power spectrum Eo(f) of the measuring system by using a standard reflector positioned in the region equivalent to be measured in a non-attenuative medium; (c) normalizing the power spectrum Er(f) obtained in step (a) with the power spectrum Eo(f) to obtain the transfer function R(f) of a living body tissue, at the region to be measured; (d) obtaining the transfer function R(f) at a particular frequency fo; (e) obtaining P(f) by normalizing R(f) with R(fo) at the particular frequency fo; (f) obtaining P(f)/A(f) by dividing P(f) obtained in step (e) with A(f), utilizing the fact that the function Q(f), which is the transfer function R(f) of a living tissue model, normalized with its specific value at fo is expressed in the form of EQU Q(f)=A(F)*e.sup.B(f), (g) expressing the function obtained in step (f) using logarithmic operators; and (h) obtaining the optimum values of parameters of the functions A(f) and B(f) using regression processing such that the function obtained in step g is considered to be equal to the function B(f).