In this report, the authors state about the results of a forced oscillation test and its measuring device. A method of determining the coefficients of equations of ship motions is presented when the equations for heave and pitch are given in eqs. (1) and (2). As an example, virtual mass coefficients, damping coefficients, coefficients of restoring functions, coupling factors and non-linear factors were determined for a 2·5 m model of super tanker. The exciting forces and moments of waves acting on the ship model were also measured. The authors made clear the phenomena in the neighbourhood of the critical frequency of motion.