In order to predict the formation of ferroelastic phases in crystal grains of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), which is a common material used for solid oxide fuel cells (SOFCs), we propose an analysis method based on a phase-field model. The phase-field model equipped with the elastic energy is introduced to realize the ferroelastic phase formation in a crystal grain. The finite element method (FEM) is employed to solve the phase transformation, and strain distributions are also calculated by FEM. On the basis of the developed analysis method, some numerical examples of analysis are performed to reproduce the deformation-induced nucleation and growth of ferroelastic phases of LSCF. The microstructures obtained from the simulations are varied in accordance with the initial microstructure and their tendencies are discussed. These microstructures are reproduced by the proposed analysis method based on finite element method, which enables us to evaluate the deformation field in terms of changes of shape and stress.