Carrying out quantum chemical calculations, we examined the excitation-energy transfer (EET) in a diphenylethyne-linke porphyrin array. The calculations showed that this transfer is caused by nonadiabatic interaction induced by the rotation around the porphyrin-diphenylethyne bond. This result is consistent with our theory that regards, in contrast to Forster's theory, the EET as a nonadiabatic transition.