The present invention provides a dental arch measuring device including: a first main body whose two ends are respectively provided with a first pivoting hole and a first positioning portion, wherein an arc-shaped limiting hole is defined above the first pivoting hole, and a horizontal arch-shaped first scale and a vertical second scale are installed between the limiting hole and the first positioning portion； and a second main body whose two ends are respectively provided with a second pivoting hole and a second positioning portion, wherein a limiting member and an indicating member are installed between the second pivoting hole and the second positioning portion. The second main body is superimposed on the first main body, and the second pivoting hole corresponds to the first pivoting hole and provides a pivot for insertion. The limiting member is penetratedly installed in the limiting hole to allow the indicating member to point at the first scale, thereby placing the first positioning portion and the second positioning portion on teeth to respectively measure the width and depth of the dental arch from the first scale and the second scale.本發明牙弓測量器，其包括：一第一本體，其兩端分別設有一第一樞接孔及一第一定位部，該第一樞接孔的上方設有一弧形的限位孔，該限位孔與該第一定位部之間具有設一橫向且弧形的第一刻度計及一縱向的第二刻度計；以及一第二本體，其兩端分別設有一第二樞接孔及一第二定位部，該第二樞接孔與該第二定位部之間設有一限位件及一指示件，該第二本體係疊合於該第一本體上，該第二樞接孔與該第一樞接孔對應，並提供插設一樞軸，該限位件係穿設於該限位孔中，使該指示件指向該第一刻度計，藉此將第一定位部與第二定位部放置於牙齒上，由第一刻度計與第二刻度計分別測得牙弓的寬度與深度。
