Dementia with Lewy bodies (DLB) usually presents with progressive cognitive decline and parkinsonism. We report a 68-year-old man who showed parkinsonism including resting tremor and mild cognitive decline. After anticholinergic medication, he showed recurrent visual hallucination. Neuropsychological tests revealed frontal and memory impairments. PET showed hypometabolism in the primary visual and visual association cortices. It is necessary to consider the possibility of DLB as well as anticholinergic side effect when visual hallucination occurs during the treatment of parkinsonism.