An exterior structure for a wire harness is provided with a pipe that has an electric wire insertion space that allows an electric wire to be inserted through the inside of the pipe. The pipe includes a diameter reduction portion that is defined by an inward deformation of the pipe in a diameter direction that narrows the electric wire insertion space. In the diameter reduction portion, the clearance between (i) the electric wire that is inserted through the electric wire insertion space of the pipe and (ii) the inner circumferential surface of the pipe can be reduced or eliminated, which suppresses rattling of the electric wire.