Authors measured the launching force by a new method. The method is as follows: The launching force was obtained by observing the change of current due to the change of magnetic flux in the search coil around a Ni-Cr-Mo steel bar of 28m/m diametre and 470m'm length, attached in the ram of the hydraulic trigger and compressed by the launching force. Applying this method to the “Steel Ball Launching” of several ships, authors show the statical fricitional coefficient is about 0.020.