The purpose of the present invention is to provide a technology which makes it possible to easily secure a separately formed wire harness to a muffler. The wire harness securing structure is equipped with: a muffler positioned between a body and a floor mat in a vehicle; a wire harness positioned along the principal surface of the muffler; and a securing member which secures the wire harness to the muffler by passing through a through-hole formed so as to pass through the muffler in the thickness direction thereof. The inner-circumferential surface of the through-hole in the muffler is adhered to the securing member.