A pneumatic tire includes a circumferential main groove extending in a tire circumferential direction in a tread surface of a tread portion, wherein when the circumferential main groove is segmented into an outer side in a tire radial direction and an inner side in the tire radial direction by drawing an imaginary segment line parallel with a straight line connecting each of groove opening edges at a position of ½ of a groove depth in a meridian cross-section, a cross-sectional area SU on the outer side in the tire radial direction and a cross-sectional area SD on the inner side in the tire radial direction satisfy the relationship 0.15≤SD/SU≤0.60.