A sheathing member mounting apparatus is provided with a support mechanism that supports a sheet member from the side of a protective layer, electric wire holding mechanisms that hold an electric wire portion in a state of being disposed along a bonding layer of the sheet member, and a folding mechanism that folds the sheet member in two. A second region supported by a second support portion is pivoted toward a first support portion, whereby the electric wire portion of a wire harness is sandwiched in the folded sheet member to be covered.