The statical longitudinal bending moment acting on a ship is affected by many factors, which relate mutually. In spite of existing this relation, the functional expression which describes sufficiently how the bending moment depends upon all these factors supposed to concern it seems to have not yet been accepted. The author studied this functional relation using two non-dimensional quantities : “load distribution coefficient κ” and “weight-displacement ratio ω”, as stated in the technical report No. 3 of the Nippon Kaiji Kyokai. In Section II, the calculation formulae for the bending moment at midship are expressed using κ and ω due to each affecting component. In Section III, based on the relations obtained in Section II, the effects of the various factors which mainly affect to the bending moment at midship are examined, such as fineness, hull and outfit weight, weight in machinery space, weight in pump space, amount of fuel and fresh water, amount of cargo weight, position and length of machinery space, position and length of cargo hold in superstructures. In Section IV, the characteristics of the bending moment at midship which are inherent to the kind and type of ship are clarified. In Section V, by considering its preferable characteristics, the optimum general arrangements of ships are discussed from the point of view of the statical longitudinal bending moment.