To provide a different-diameter pipe clamping structure of a pipe clamp, which can stably and positively fasten pipes of different diameters.

The pipe clamp 1 is formed by connecting together one ends of a pair of arcuate pinching pieces 4, 5 via a hinge 6, forming projective pieces 8, 9 on the other ends so as to be opposed to each other, and fastening a bolt 7 penetrating through holes 10 formed in the respective projecting pieces, by a nut. Herein the projecting piece 9 on the side of a head of the bolt 7, has arcuately bulging bearing portions 13 formed on a surface thereof at locations on both lateral sides of the through hole along a projecting direction of the projecting piece 9, for bearing a rear surface of the bolt head 7a.