A 31-year-old man presented to our clinic for an ocular trauma to his left eye. His best-corrected visual acuity was 20/200 OS (left eye). Anterior segment examination showed an epithelial defect, which implies a direct injury to the cornea. A marked focal stromal edema accompanied by Descemet's membrane folds were located at 10 o'clock in the paraxial area, about 4 mm apart from the corneal center. Anterior segment optical coherence tomography (AS-OCT) revealed marked corneal swelling of the lesion. Five days later, the patient's best-corrected visual acuity improved to 20/50 OS. The stromal edema resolved showing no signs of epithelial defect, although small opacity remained. AS-OCT revealed complete resolution of corneal swelling. Despite the resolution of corneal edema, however, specular microscopy showed substantially decreased endothelial cell density in the lesion compared to the fellow eye. Here we report a case of traumatic corneal stromal edema discovered by AS-OCT.