Introduction: Oral melanotic macule (OMM) is a benign discoloration of oral mucosa that is identified by an increase in melanin pigmentation. The diagnosis of OMM is critical because it may have a similarity to oral melanoma at early stages. Therefore, microscopic examination is necessary to confirm the accurate diagnosis of the OMM. Case Presentation: We report two cases of discoloration in the oral cavity with asymmetry and border irregularity. After obtaining informed consent, we performed an excisional biopsy that showed the increase of melanin adjacent to the basal and parabasal layers of squamous epithelial cells, confirming the diagnosis of OMM. Conclusions: Early melanoma can have a similar clinical appearance to OMM. Therefore, an excisional biopsy can be done and the diagnosis of OMM can be confirmed by microscopic examination.