Primary tumor of the appendix is a rare disease entity of gastrointestinal malignancy. Most of them are discovered unexpectedly in an acute situation. The diagnosis of adenocarcinoma of the appendix is hardly made preoperatively. An unsuspected finding of appendiceal tumor during operation can cause confusion about appropriate management of the lesion. The prognosis of adenocarcinoma of appendix can be determined by Dukes' stage and is similar, stage for stage, to that of colorectal carcinoma. We experienced a patient with linitis plastica type of primary adenocarcinoma of the appendix, who complained right lower quadrant pain for twenty days. The patient underwent appendectomy only. The second curative operation could not be performed due to patient's condition.