The 1994 Hokkaido-Toho-Oki Earthquake of JMA (Japan Meteorological Agency) Magnitude 8.1 occurred in east off Hokkaido island in Japan at 22:22:56, October 4,1994. This earthquake triggered 30 accelerographs installed at 19 ports in the strong-motion earthquake observation network of the Port and Harbour Research Institute. 20 accelerograms out of 30 were obtained as digital acceleration data of three components observed in port areas in Japan. 　This report presents the strong-motion earthquake observation results of this earthquake and the results of preliminary analyses of the 17 digitized acceleration records obtained on and in ground by the main shock. The records of the after shock at 22:42:51, October 4,1994, at 05:39:51, October 6,1994 and at 16:55:39, October 9,1994 are also presented. Original acceleration without instrument correction, corrected acceleration with instrument correction, SMAC-B2 equivalent acceleration, integrated velocity and displacement, response spectra, Fourier spectra and loci of accelerations, velocities and displacements are presented as results of preliminary analyses. Amplification of accelerations of the main shock at Kushiro port are also presented because surface ground motion and base motion were observed simultaneously ther. Attenuation relations of acceleration, velocity and displacement of the main shock are also presented in this report.