A study was carried out to obtain the dimensions of main members in wooden ships after modifying the standard strength calculation, because an urgent need occured to revise the existing “Wooden Ship Construction Rule” in order to fit present situation. Calculating the longitudinal and transverse stength by means of simple beam theory, basic dimensions of each member were obtained with newly determined allowable stress of wood. Then multiplying the rate of stress increase (construction coefficient), which was unavoidable in the lattice-like construction of the wooden ships containig many joints, by basic dimensions, the actual dimensions were obtained. As compared with those of existing “Rule”, the newlyobtained actual dimensions showed satisfactory results.