A stud pin embeddable in a pin embedding hole provided in a tread portion of a pneumatic tire , the stud pin comprising: a tip including a tip end surface configured to come into contact with a road surface ; and a trunk portion that supports the tip and extends in one direction, the trunk portion including: an upper flange disposed at a first end of the trunk portion , the tip being fixed to the upper flange ; and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion ; wherein an upper end surface of the upper flange from which the tip protrudes includes a recessed surface , the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip , wherein in a cross section of the upper flange and the tip taken along a plane parallel to and including a central axis of the tip that extends in an extending direction of the trunk portion , the cross section being represented in an X-Y coordinate system where the extending direction toward the tip end surface is defined as a y direction, a direction orthogonal to the extending direction extending outward from the stud pin is defined as an x direction, and a position of the protruding base portion of the tip is defined as an origin point of the X-Y coordinate system, an inclination angle with respect to an x direction at a discretionary position D on a curved or a straight line corresponding to the inclined surface is larger than an inclination angle with respect to the x direction at a same position in the x direction as the position D on a parabola, the parabola passing on the origin point and having a focus point at a point on the tip end surface that is located at a same position in the x direction as the origin point. a tip including a tip end surface configured to come into contact with a road surface ; and a trunk portion that supports the tip and extends in one direction, the trunk portion including: an upper flange disposed at a first end of the trunk portion , the tip being fixed to the upper flange ; and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion ; wherein an upper end surface of the upper flange from which the tip protrudes includes a recessed surface , the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip , wherein an upper flange disposed at a first end of the trunk portion , the tip being fixed to the upper flange ; and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion ; wherein in a cross section of the upper flange and the tip taken along a plane parallel to and including a central axis of the tip that extends in an extending direction of the trunk portion , the cross section being represented in an X-Y coordinate system where the extending direction toward the tip end surface is defined as a y direction, a direction orthogonal to the extending direction extending outward from the stud pin is defined as an x direction, and a position of the protruding base portion of the tip is defined as an origin point of the X-Y coordinate system, an inclination angle with respect to an x direction at a discretionary position D on a curved or a straight line corresponding to the inclined surface is larger than an inclination angle with respect to the x direction at a same position in the x direction as the position D on a parabola, the parabola passing on the origin point and having a focus point at a point on the tip end surface that is located at a same position in the x direction as the origin point. <EOS>