Abstract State energies of the cinnamaldehyde molecule are calculated by the simple LCAO-MO method, including configuration interaction and assuming the C2v symmetry. The results of the calculation conform well with the observed absorption bands lying in the 2000∼3000 Å region. In cinnamaldehyde the 280 mμ band is assigned to the intramolecular charge transfer band. The B2− band which we could not find in spectrum of cinnamaldehyde may be covered under the charge transfer band which is greatly shifted toward the red as the result of extension of conjugation. In the region of the band IIc two peaks at 224 and 218 mμ represent two different transitions, respectively. The former is assigned to the B2+ type transition and the latter to the transition in the acrolein group.