The main objective of the research work is to present the free vibration analysis of plates composed of one of the materials that have good performance and can be applied in many fields like buildings. Material that has such properties is Functionally Graded Material (FGM). FGM consists of a mixture of ceramics and metals through varying volume fractions, ceramic material as a heat barrier at the high-temperature side, and metal material with rigid properties and high conductivity at the low-temperature side. In this paper, the FGM plate is investigated using the finite element method. We use 3-node Triangular Mixed Interpolation of Tensorial Components (MITC3), widely used by researchers or commercial software. The MITC3 element is a triangular element that gives good performance to analyze plate problems, especially isotropic plate problems. We performed the numerical analysis to examine the performance and convergence behavior of the MITC3 FGM plate element in the case of rectangular plates with varying length to width ratios, and the results are compared with the reference solution.