To provide a dental treatment chair which makes one unit thereof applicable for adults and children flexibly and enables setting thereof to fit the somatotype of patients in application.

The numeral 10 in the figure indicates a back rest part and 20 a contour seat part. The back rest comprises three stages 11, 12 and 13, upper, middle and lower and the contour seat part 20 comprises three stages 21, 22 and 23, upper, middle and lower. The middle parts 12 and/or 22 (shaded) are made free to detach. Fig. 1 (A) shows the configuration for adults (large) and Fig. 1 (B) the conversion of the large size of the dental treatment chair as shown in Fig. 1 (A) to that for children (small) Fig. 1 (C) shows the configuration for children (small). This enables dental treatment by shifting the size (state) of the dental treatment chair to fit the somatotype of the patient, i.e., to the state shown in Fig. (A) when the patient is an adult or to the state shown in Fig. 1 (C) when the patient is a child.