The association of normal pressure hydrocephalus (NPH) with Alzheimer’s disease (AD) is not uncommon. However, we herein report a rare case of AD that showed severe NPH at the late stage of AD. A 74-year-old woman developed forgetfulness without motor disturbances at 56 years old and was diagnosed with AD because of imaging findings showing atrophy of the fronto-temporo-parietal lobes on magnetic resonance imaging (MRI) and a decrease in the regional cerebral blood flow (rCBF) of the frontotemporo-parietal lobes on single-photon emission computed tomography (SPECT). Eight years later, she showed progressive rigidity and akinesia of the arms and legs suggestive of parkinsonism, along with intermittent myoclonus of the arms, both more marked on the right. Her myoclonus was moderately controlled by oral clonazepam. She became bed-ridden at 74 years old and was admitted to our hospital (Tokuyama Medical Association Hospital) for endoscopic gastrostomy. At this time, head computed tomography showed severe NPH based on the radiological diagnostic criteria of idiopathic NPH (iNPH). We concluded no indication of ventriculoperitoneal shunt operation because of her severe dementia, and then she was transferred to a nursing home. This case is interesting, as the NPH imaging findings that appeared at the late stage of AD were striking. Her severe parkinsonism might have been due in part to NPH, although the myoclonus was considered to be of AD origin. Sequential radiological studies are useful for clarifying the clinical manifestations of AD patients.