All six carbon-carbon bonds in benzene are of the same length, at 140 (pm). The C-C bond length are greater than a double bond (135 pm) but shorter than a single bond (147 pm). This intermediate distance is consistent with electron delocalization the electrons for CC bonding are distributed equally between each of the six carbon atoms.
Concept of benzene ring resonance
Benzene is a hybrid of various resonating structures .The hybrid structure is represented by inserting a circle or a dotted circle in the hexagon.The circle represents the six electrons which are delocalised between the six carbon atoms of the benzene ring.