The effects of particle loss and energy loss on ECCD have been investigated by using a steady-state linear Fokker-Planck equation. These ECCD efficiencies are shown to be easily obtained by the adjoint methods and are explicitly calculated by taking into account the relativistic effect on the electron-cyclotron resonance condition. With decreasing the characteristic loss time, the ECCD efficiency is found to be considerably reduced. The reduction rate depends on the values of the normalized parallel velocity of resonant electrons and the relativistic parameter which represents the strength of the relativistic correction to the resonance condition.