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 (X) 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 (X), 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 (X), 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 (X), 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 (X) 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 (X), 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 (X), 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 (X), as viewed from the axial direction. <EOS>