A pipe bend die unit comprises a clamp member having a first groove part of half-circular cross section on an outer peripheral surface thereof with a fitting recess extending in a peripheral direction by a first predetermined length on a planar surface perpendicular to a rotary axis, and a counter pressure member having a second groove part of half-circular cross section formed on an outer peripheral surface thereof, and a fitting protrusion extending in a peripheral direction by a second predetermined length from a tip end portion of the second groove part. The fitting protrusion is positioned in the fitting recess so that the first and second groove parts are combined to form a pipe-receiving groove of half-circular cross section. The counter pressure member and the clamp member are hingedly connected to one another so as to be rotatable relative to each other about the rotary axis.