A 73-year-old women visited emergency department because of sudden right hemiplegia. She had a history of duodenum papilla cancer terminal stage and multiple liver metastasis. On admission, diffusion weighted images revealed high intensity area at left middle cerebral artery territory. In addition, 3D-TOF MRA depicted proximal part of the left internal carotid artery. We performed endovascular thrombectomy because low platelet count met contraindication of intravenous recombinant tissue plasminogen activator therapy. Although we could get partial recanalization of middle cerebral artery occlusion after thrombectomy, the patient eventually died due to multiple organ failure. Autopsy findings showed white thrombus on mitral valve and also left middle cerebral artery occluded by similar white thrombus without infective findings. The patient was finally diagnosed with nonbacterial thrombotic endocarditis due to white thrombus on the mitral valve. We should select appropriate mechanical thrombectomy devices with a case of cerebral infarction due to nonbacterial thrombotic endocarditis because its thrombus is often white thrombus and would be hard.