From the view point of study of safety at launching work and design of launching trigger, it is quite indispensable to grasp the accurate magnitude of starting force of ship at launching. Authors tried to measure actually the starting force of ship by means of magneto-striction type pressure gauge placed between launching trigger and hydraulic ram. The magnitude of starting force thus measured by authors are much greater than that calculated from the theory and the data accepted up to now, and we discovered that the apparent frictional coefficient calculated conversely from the measured starting force lies between 0.005 and 0.012. We believe the magnitude of actual starting force depend not only upon the quality of grease, but upon the quality and quantity of soft soap and especially upon the exposed scope of grease. The value of frictional coefficients gained by authors are that considered the all factors mentioned above.