Recently, the matrix method has become almost universal tool to solve various engineering problems in conjunction with the rapid development of high speed electronic computers. The method also has been introduced to ship structure analysis in past few years. This paper treats a method to obtain an approximate solution for stress distribution in a web frame of oil tankers. The method is designed to use relatively small computer. The procedure consists of two steps. In the first step, the web frame is idealized to a plane frame of slender members as shown in Fig. 2. Then, the plane frame is analyzed with a matrix method to determine forces and moments in each members. In the second step, the original shape of the web frame is restored and any portion of the frame, in which the stress distribution is desired, is isolated as shown in Fig. 3. Then, again, a finite element method is used to determine the stress distribution in the isolated portion. In this work, IBM 1130 computer in the computation center, SUN has been used. A numerical example with scantlings of an actual ship is worked out to prove the validity of this method.