Crystal structure and electronic structure above and below the metal-insulator phase transition temperature(T(MI) = 200K) were examined for organic charge transfer complex alpha-(BEDT-TTF)2Cu(NCS)2. The temperature dependence of the lattice constants showed an anomaly around T(MI). The electronic band structure showed a semimetallic character at room temperature, and the suppression of that character at 104 K was also shown. The nature of the metal-insulator phase transition was discussed.