Abstract: A mouth corner spreader used for spreading both corners of the mouth for facilitating medical examination, treatment, photographing or other works in the mouth. The device comprises a pair of hook structures arranged in opposed relation to each other and designed to fit to the mouth corners, each of said hook structures consisting of a substantially C-shaped external portion, a substantially C-shaped internal portion provided spaced-apart from said external portion and a joining portion joining said external and internal portions along the inside edges of the C-shaped portions, and a substantially U-shaped elastic spring arm connecting said pair of hook structures.