To provide a mouthpiece which is excellent in followability when a force is added to a fitting member by grinding of the teeth or the like and is highly comfortable in the mouth.SOLUTION: A mouthpiece 10 includes: a first piece 1 having first through holes on left and right outer wall parts； a second piece 2 having second through holes on the left and right outer wall parts； a first fitting member 3 which has a first base part that is inserted in the left and right first through holes and exposed without protruding from the wall surface on the tooth row side of the outer wall part and a first fitting part protruding from a wall surface opposite to the tooth row side of the outer wall part； a second fitting member 4 which has a second base part that is inserted in the left and right second through holes and exposed without protruding from the wall surface on the tooth row side of the outer wall part and a second fitting part protruding from the wall surface opposite to the tooth row side of the outer wall part； and a connection member 5 which has a first connection part and a second connection part fitted to the first fitting part and the second fitting part and openably connects the first piece and the second piece.SELECTED DRAWING: Figure 1【課題】歯軋りなどにより取り付け部材に力が加わった際の追従性に優れ、口内快適性の高いマウスピースを提供する。【解決手段】第１貫通孔を左右の外壁部に有する第１ピース１と、第２貫通孔を左右の外壁部に有する第２ピース２と、左右の第１貫通孔に挿入され、外壁部の歯列側の壁面から突出せずに露出する第１ベース部及び外壁部の歯列側とは反対側の壁面から突出する第１取り付け部を有する第１取り付け部材３と、左右の第２貫通孔に挿入され、外壁部の歯列側の壁面から突出せずに露出する第２ベース部及び外壁部の歯列側とは反対側の壁面から突出する第２取り付け部を有する第２取り付け部材４と、第１取り付け部及び第２取り付け部に取り付けられる第１連結部及び第２連結部を有し、第１ピースと第２ピースとを開閉可能に連結する連結部材５と、を備えたマウスピース１０。【選択図】図１
