The aerodynamic heating has significant influences on the flutter characteristics of fins of sounding rockets in a high supersonic range. In the present report, some calculations of flutter of plate fins are presented. Increases in temperature of fins are estimated by a heat transfer calculation according to mission profiles of rockets. Considering the reduction in Young's modulus of materials and stiffness of fins due to these increases in temperature, the flutter dynamic pressure is calculated by the direct method of variational approach. It is shown that the flutter dynamic pressure is decreased markedly when the effect of aero-dynamic heating is taken into account, and the flutter margin of fins of sounding rockets is clarified concretely.