An experiment to estimate bottom geoacoustic properties was conducted in the coastal area of Gulf Suruga off Numazu in August 1995. The measurements were made at a 70-m-depth site using a vertical line array of 12 receivers spaced at 5-m intervals. A cw source output at 55 Hz with 167 dB re: 1 (mu)Pa source level was towed at a constant depth over 3 km in horizontal range along the coast. Acoustic fields measured by a synthetic array at each channel were processed with a Hankel transform, whose output wave-number spectrum provided several peaks corresponding to mode eigenvalues. The position of each peak, however, varies slightly depending on the channel; this variation is considered to be caused by the range dependence of the waveguide and/or by mutual interaction of adjacent mode spectrum due to the finite aperture. Applying an inversion method to the observed mode eigenvalues, bottom geoacoustic parameters (sound speed, attenuation, and density) were estimated under several assumptions. Propagation loss calculated with use of the estimated parameters was found to be in good agreement with the observed one.