Stiffened plates, mostly used in the major part of ship and airplane structures, have been studied by various way-theoretical and experimental. In case of the fore and aft parts of the parallel middle body of ship structure, the stiffeners are not right-angled to the plate but acute angled. This paper presents the analysis of plates having included stiffeners by Finite Strip Method. The results of calculation show the influence of inclined angle which is less than $10^{circ}$is ignorable. It is recommended that, when the inclined angle is over $20^{circ}$, the section modulus of stiffener should be increased.