Synchrotron radiation angle resolved photoemission spectroscopy measurements were performed on Ca 3 Co 4 O 9 , which is one of promising candidates for the thermoelectrical material because of its possession of the large thermoelectric power, metallic electrical conduction, and low thermal conductivity. Three dispersing bands were observed in the energy range of E = 0 – 0.9 eV below the Fermi level, and one of these bands constructs a hole-like Fermi surface (FS) centered at Γ point. These bands were successfully assigned as those from two-dimensionally spanned CoO 2 layers by observing their periodicity in the reciprocal space. It was also found that the FS possesses a hexagonal shape with its edge center aligned on the direction of the primitive reciprocal lattice vector K → . By using tight-binding fit on the band that crosses E F , we successfully reproduced the characteristic features in the density of states that is responsible for the large thermoelectric power and the metallic electrical conduction.