Patients with advanced-stage Parkinson's disease (PD) occasionally experience refractory depression or catatonic stupor. Electroconvulsive therapy (ECT) has been reported as a successful procedure for both severe psychosis and motor symptoms in patients with PD. Four patients with PD who were receiving ECT were quantitatively evaluated using the Unified PD Rating scale part III, Hoehn and Yahr scale, Barthel index, Neuropsychiatric Inventory, mini-mental state examination, Revised Hasegawa's Dementia scale, Beck's Depression Inventory, and Hamilton Rating Scale for Depression-17. We adopted the "half-age" method, which is an age-based stimulus-dosing method. The patients showed improvement in symptoms of psychosis and motor symptoms without any adverse effects. The interval of improvement after ECT varied among patients. Of note, a decrease in psychiatric symptoms successfully alleviated the burden of caregivers. ECT may be useful to treat parkinsonism with refractory psychosis, major depression, or catatonic stupor, within the limitations of the patients enrolled.