Reconstruction techniques of orofacial defects caused by wide excision of the intraoral malignant lesions are various. Although radial forearm free flap is a common donor site on reconstruction of soft tissue defect, anterolateral thigh (ALT) free flap also has an established site in orofacial soft tissue reconstruction as the favored donor flap with recent progress of the microsurgical technique. A 59-year-old female complained of hyperplastic mass on the right retromolar and buccal cheek, which was diagnosed as a squamous cell carcinoma (SCC) by an incisional biopsy. Before the operation, we planned a wide excision of the SCC lesion, supraomohyoid neck dissection, reconstruction with radial forearm free flap (RFFF), and split thickness skin graft. We accidentally found an arterial variation of the forearm area during elevation of RFFF, and changed the plan of reconstruction operation to reconstruction with ALT free flap. Operative sites was healed well during the post-operative period, and we referred to the department of radiation oncology for post-operative radiotherapy.