A mat mounting structure for mounting a mat on a seat back frame in a seat back may have a guide wire attachable to the mat configured to receive a force from a back of an occupant on the seat back. The guide wire may have a straight part extending linearly in a longitudinal direction of the seat back frame on a head side or a root side of the seat back frame. A bushing including a penetration hole in which the straight part is insertable in the longitudinal direction may be included in the structure. An attachment hole part in the seat back frame may also be part of the structure. The bushing may be detachably engageable with and attachable to the attachment hole part.