The invention provides a headrest for a dental treatment chair and a dental treatment chair wherein discomfort due to noise generated from dental treatment instruments can be reduced and communication between a dentist and a patient can be ensured.The headrest for the dental treatment chair and the dental treatment chair comprise a back head supporting member 91 for supporting a back of the head of the patient during dental treatment and ear supporting members 92 and 92 which can be bent in directions to cover ears of the patient at both ends of the back head supporting member 91. The ear supporting members 92 and 92 or the back head supporting member 91 has sound output sections 93 and 93 each for outputting a sound from a sound source, and the ear supporting members 92 and 92 have a sound collecting section 94 for collecting sounds in a surrounding environment. Acoustic filters 95 and 95 cut off frequencies higher than 8 kHz from a sound signal collected by the sound collecting section 94.