A stud pin to be embedded in a pin embedding hole provided in a tread portion of a pneumatic tire, the stud pin comprising: a tip comprising a tip end surface configured to come into contact with a road surface; and a body portion provided around a center axis of the stud pin and configured to support the tip; the body portion comprising: an upper flange configured to fix the tip at a first end of the body portion; a lower flange provided on a position on a side opposite to the first end of the body portion; and a shank portion configured to connect the upper flange and the lower flange, characterized in that the lower flange comprises a first side surface extending parallel with an axial direction of the center axis, the first side surface comprises a first curved surface recessed inward in relation to the body portion, as viewed from the axial direction, the upper flange comprises a second side surface extending parallel with an axial direction of the center axis, the second side surface comprises a second curved surface bulging toward a periphery of the body portion as viewed from the axial direction, and a pair of third curved surfaces or flat surfaces configured to connect the second curved surface to interpose the second curved surface, each of the pair of third curved surfaces or the flat surfaces having a smaller curvature along a periphery of the second side surface orthogonal to the axial direction than a curvature of the second curved surface, and a trough portion where the first curved surface is most recessed and a peak portion where the second curved surface is most bulged being located at an identical orientation position about the center axis, as viewed from the axial direction. a tip comprising a tip end surface configured to come into contact with a road surface; and a body portion provided around a center axis of the stud pin and configured to support the tip; the body portion comprising: an upper flange configured to fix the tip at a first end of the body portion; a lower flange provided on a position on a side opposite to the first end of the body portion; and a shank portion configured to connect the upper flange and the lower flange, an upper flange configured to fix the tip at a first end of the body portion; a lower flange provided on a position on a side opposite to the first end of the body portion; and a shank portion configured to connect the upper flange and the lower flange, characterized in that the lower flange comprises a first side surface extending parallel with an axial direction of the center axis, the first side surface comprises a first curved surface recessed inward in relation to the body portion, as viewed from the axial direction, the upper flange comprises a second side surface extending parallel with an axial direction of the center axis, the second side surface comprises a second curved surface bulging toward a periphery of the body portion as viewed from the axial direction, and a pair of third curved surfaces or flat surfaces configured to connect the second curved surface to interpose the second curved surface, each of the pair of third curved surfaces or the flat surfaces having a smaller curvature along a periphery of the second side surface orthogonal to the axial direction than a curvature of the second curved surface, and a trough portion where the first curved surface is most recessed and a peak portion where the second curved surface is most bulged being located at an identical orientation position about the center axis, as viewed from the axial direction.