We performed the optical spectroscopic observation of a classical nova V5588 Sgr on Apr. 12. The spectrum exhibits the emission lines of Balmer series, HeI, OI, CaII and FeII. We also possibly identified the CII emission line at 7234 A. The identification of HeI and CII indicates that the photosphere of the nova evolved after the earliest report by Arai et al. (CBET 2679). We will observe this object.