To provide a mat-shaped seat for a dental chair which can be also effectively applied to children and elderly persons, because the conventional simple pad and headrest cover with a pillow for the neck which are put on the dental chair, can be applied only to adult patients and lowly effective for the children and elderly persons with low height and sitting height.

In the mat-shaped seat for the dental chair, a mat-shaped seat for a sitting part, a mat-shaped seat for legs and a mat-shaped seat for a backrest part longitudinally divided into two parts, an upper part and a lower part, which cover each section of the chair body, are flexibly combined and united through joining means respectively, and furthermore, a plurality of raft-shaped balloons which can be expanded and contracted by air are collaterally arranged on reverse sides of the mat-shaped seat for the legs and an upper part of the mat-shaped seat for the backrest part.