A sheathing member mounting apparatus for covering an electric wire portion of a wire harness with a sheathing member formed of a sheet member that is formed in a shape of a sheet where a bonding layer is provided on one surface and a protective layer is provided on the other surface, the sheet member including a protruding member that protrudes from the protective layer and being mountable to a fixed body by engagement of the protruding member; the apparatus comprising: a support mechanism that supports the sheet member from a side of the protective layer; an electric wire holding mechanism (3, 4) that holds the electric wire portion in a state of being disposed along the bonding layer of the sheet member supported by the support mechanism; and a folding mechanism that folds in two the sheet member supported by the support mechanism, wherein the support mechanism includes: a first support portion that supports a region substantially half of a plane of the sheet member; and a second support portion that supports a remaining region of the sheet member other than the region substantially half of the plane, and the remaining region of the sheet member is pivoted toward the first support portion by the folding mechanism, whereby the sheet member is folded and the electric wire portion is sandwiched under a condition where the bonding layer is on an inside and covered by the bonding layer being bonded together, the apparatus being characterized in that at least one concave portion for receiving the protruding member is formed on at least one of the first support portion and the second support portion, and the at least one concave portion is provided in a predetermined position in a direction of the plane of the sheet member or formed on a receiving member which is provided so as to be movable in a direction of the plane of the sheet member. a support mechanism that supports the sheet member from a side of the protective layer; an electric wire holding mechanism (3, 4) that holds the electric wire portion in a state of being disposed along the bonding layer of the sheet member supported by the support mechanism; and a folding mechanism that folds in two the sheet member supported by the support mechanism, wherein the support mechanism includes: a first support portion that supports a region substantially half of a plane of the sheet member; and a second support portion that supports a remaining region of the sheet member other than the region substantially half of the plane, and the remaining region of the sheet member is pivoted toward the first support portion by the folding mechanism, whereby the sheet member is folded and the electric wire portion is sandwiched under a condition where the bonding layer is on an inside and covered by the bonding layer being bonded together, the apparatus being characterized in that at least one concave portion for receiving the protruding member is formed on at least one of the first support portion and the second support portion, and the at least one concave portion is provided in a predetermined position in a direction of the plane of the sheet member or formed on a receiving member which is provided so as to be movable in a direction of the plane of the sheet member.