A pneumatic tire, comprising: a tread portion with an annular shape that extends in a tire circumferential direction; a pair of sidewall portions disposed on either side of the tread portion; a pair of bead portions disposed toward the inside of the sidewall portions in a tire radial direction; a bead core disposed in each one of the pair of bead portions; a carcass layer mounted between the pair of bead portions; and a side reinforcing layer having a crescent-shaped cross-section disposed toward the inside in a tire lateral direction of the carcass layer at each one of the pair of sidewall portions, wherein the bead core comprises at least one bead wire wound in the tire circumferential direction, in a meridian cross-section, a plurality of circumferential portions of the bead wire form at least one row in line in the tire lateral direction and a plurality of layers layered in the tire radial direction, in a meridian cross-section, an external contour shape of the bead core is a polygon formed by common tangent lines of the circumferential portions of the bead wire, the external contour shape comprises a single vertex Q located toward the outside in the tire radial direction, an internal angle θ1 formed by two sides sandwiching the vertex Q is an acute angle, and the external contour shape comprises a bottom side located toward the inside in the tire radial direction at a position opposite the vertex Q and extending in the tire lateral direction, the carcass layer comprises a body portion that extends from the tread portion, through a sidewall portion of the pair of sidewall portions, to a bead portion of the pair of bead portions, and a folded back portion that is bent and folded back along a circumference of the bead core in each one of the bead portions and extends from a position of an outer end of the bead core in the tire radial direction toward one of the pair of sidewall portions in contact with the body portion, and a straight line extending in the tire lateral direction through the vertex Q is defined as a straight line L1, a straight line extending in the tire radial direction through the vertex Q is defined as a straight line L2, characterized in that an arc constituting a profile of a portion of a tire exterior surface of the outer side in the tire lateral direction located on an extension line of the straight line L1 is defined as an arc R, a center O of the arc R exists outside the tire exterior surface in the tire lateral direction, a distance in the tire radial direction between the center O of the arc R and the straight line L1 is within 20% of a radius r of the arc R, and a distance in the tire lateral direction between the center O of the arc R and the straight line L2 with respect to the radius r of the arc R is within a range of 2r ± 0.4r. a tread portion with an annular shape that extends in a tire circumferential direction; a pair of sidewall portions disposed on either side of the tread portion; a pair of bead portions disposed toward the inside of the sidewall portions in a tire radial direction; a bead core disposed in each one of the pair of bead portions; a carcass layer mounted between the pair of bead portions; and a side reinforcing layer having a crescent-shaped cross-section disposed toward the inside in a tire lateral direction of the carcass layer at each one of the pair of sidewall portions, wherein the bead core comprises at least one bead wire wound in the tire circumferential direction, in a meridian cross-section, a plurality of circumferential portions of the bead wire form at least one row in line in the tire lateral direction and a plurality of layers layered in the tire radial direction, in a meridian cross-section, an external contour shape of the bead core is a polygon formed by common tangent lines of the circumferential portions of the bead wire, the external contour shape comprises a single vertex Q located toward the outside in the tire radial direction, an internal angle θ1 formed by two sides sandwiching the vertex Q is an acute angle, and the external contour shape comprises a bottom side located toward the inside in the tire radial direction at a position opposite the vertex Q and extending in the tire lateral direction, the carcass layer comprises a body portion that extends from the tread portion, through a sidewall portion of the pair of sidewall portions, to a bead portion of the pair of bead portions, and a folded back portion that is bent and folded back along a circumference of the bead core in each one of the bead portions and extends from a position of an outer end of the bead core in the tire radial direction toward one of the pair of sidewall portions in contact with the body portion, and a straight line extending in the tire lateral direction through the vertex Q is defined as a straight line L1, a straight line extending in the tire radial direction through the vertex Q is defined as a straight line L2, characterized in that an arc constituting a profile of a portion of a tire exterior surface of the outer side in the tire lateral direction located on an extension line of the straight line L1 is defined as an arc R, a center O of the arc R exists outside the tire exterior surface in the tire lateral direction, a distance in the tire radial direction between the center O of the arc R and the straight line L1 is within 20% of a radius r of the arc R, and a distance in the tire lateral direction between the center O of the arc R and the straight line L2 with respect to the radius r of the arc R is within a range of 2r ± 0.4r.