We present a case of choroidal metastasis of lung cancer in which choroidal metastasis, the first manifestation of recurrence, was successfully treated with erlotinib. A 49-year-old woman with a 2. 0 cm nodule in the right lung was diagnosed with adenocarcinoma, and a right upper lobectomy was performed. After 2 months, she presented with blurred vision of the right eye. Her right visual acuity had decreased to 0. 1, and there was a visual field defect temporal to the macula. Fundus examination of the right eye revealed an elevated mass with exudative retinal detachment temporal to the disc. Fluorescein angiography revealed hypofluorescence during the prearterial and arteriovenous phases, and fluorescein leakage surrounded by a circular hypofluorescence area during the venous phase. Spectral-domain optical coherence tomography showed exudative retinal detachment. The cancer cells had a mutation of the epidermal growth factor receptor gene in exon 19. She was treated with erlotinib at 100 mg per day, and after 4 days, her right visual acuity had improved to 1. 2.