An angle of elevation (α) of an intersection point (A), formed between a line (q) connecting intersection points (A, B) and a reference line (n) traversing a center of curvature (C) of an arc and parallel to the tire rotation axis, is from 40° to 60°, where a curve tracing the innermost region in the tire radial direction is approximated by the arc with the method of least squares, the intersection point (A) is an intersection point of the ply main body (6a) with a normal line (m) from the center of curvature (C) of the arc to a part of the ply main body (6a) convex outward in the tire width direction, and the intersection point (B) is an intersection point of the ply main body (6a) with the reference line (n). A radius of curvature of the arc is from 5 mm to 80 mm.