Several ways of quantitatively observing biological cells will be exhibited. Cells are cultured on a thin plastic film in order to make is possible to access by high-frequency acoustic beam focused onto the cell. Reflection waveform has a spectrum briefly spreading from 100 to 400 MHz. Mechanical scan makes it possible to acquire a 2-D profile. Cells in contact with the substrate can be characterized by means of characteristic acoustic impedance. In most of observations, buffer liquid that is simultaneously observed with cells may be employed as the reference material for calibration. In the process of cell culture, some of the cells may be delaminated from the substrate. In such a case significant error in acoustic impedance measurement may take place. In order to avoid such an error waveform separation is performed. As a result of such a waveform analysis, delamination distance may be calculated as well as the acoustic impedance of the cell that is slightly distant from the substrate. As an example C2C1...