Fragment ion yields in the C 1s --> Rydberg excitation region of CO2 were measured in the 90 degrees and 0 degrees directions relative to the electric vector of the Linearly polarized light. The C 1s --> ns (n = 3, 4), np pi and np sigma (n = 3-7), and nd (n = 3, 4) Rydberg transitions are clearly observed and show some vibrational structures. The dipole-forbidden C 1s(sigma(g) -- 3s sigma(g) Rydberg transition is the strongest of all the Rydberg transitions, and the ion yield in the 90 degrees direction is dominant. This indicates that the bending vibration is predominantly coupled with the 3s sigma(g) Rydberg state and the intensity-lending dipole-allowed state is a very strong pi* resonance, only 2 eV lower than the 3s sigma(g) state. On the other hand, in the 4s sigma(g) Rydberg state the vibronic coupling through the antisymmetric stretching mode is strongly observed in the 0 degrees direction. This is probably because the 4s sigma(g) state approaches another intensity-lending state with Sigma(u)(+) symmetry and goes away from the pi* resonance. The angle-resolved ion-yield technique is very powerful for elucidating the vibronic coupling mechanism.