A stress calculation method is proposed by improving the force and moment balance method to calculate the stress in semiconductor layers. The following three points are improved. The first point is that the vertically precise stress distribution in multilayers can be calculated by using imaginary thin layers. The second point is that the stress can be calculated on the basis of threedimensional deformation. The third point is that the stress can be calculated in strained layers with interfacial misfit dislocations. The stress distribution in strained semiconductor layers such as InGaAs/GaAs multilayers, InGaAs/graded lnGaAs/GaAs layers and GaAs/Si structures is calculated using this improved method.