To provide a mouthpiece in which a position adjustment part for adjusting a position at the time of occlusion between a lower jaw mouthpiece and an upper jaw mouthpiece is hardly damaged by a displacement in a right-left direction at the time of the occlusion.SOLUTION: A mouthpiece comprises: a pair of upper jaw and lower jaw mouthpieces opposed to each other； a pair of positioning members whose positions can be adjusted in a front-back direction along a guide part whose both sides are supported by a pair of fixed parts provided in one mouthpiece that is the upper jaw or lower jaw mouthpiece； and a pair of stoppers provided in the other mouthpiece of the upper jaw and lower jaw mouthpieces, and for regulating a backward displacement of the lower jaw mouthpiece by coming into contact with the positioning members.SELECTED DRAWING: Figure 9【課題】下顎マウスピースと上顎マウスピースとの咬合時の位置を調整するための位置調整部が、咬合時の左右方向の変位によっても壊れにくい、マウスピースを提供すること。【解決手段】対向する一対の上顎および下顎マウスピースと、前記上顎又は下顎マウスピースの一方のマウスピースに設けられた一対の固定部に両端が支持されたガイド部に沿って、前後方向に位置調整可能な一対の位置決め部材と、前記上顎および下顎マウスピースの他方のマウスピースに設けられ、前記位置決め部材に当接して前記下顎マウスピースの後方への変位を規制する一対のストッパと、を有するマウスピース。【選択図】図９
