The advent of human-induced pluripotent stem cell (iPSC) technology has enabled the differentiation of iPSCs derived from somatic cells of patients with various diseases into cells of disease target organs. iPSCs are suitable for drug screening using large compound libraries, as they can grow infinitely and be induced to differentiate into various types of cells. Several clinical trials have been conducted as drug repositioning for new indications of already approved drugs based on drug candidates discovered using iPSCs. The use of iPSCs can be applied not only to the discovery of drug candidates through compound screening, but also to the identification of efficacious groups in clinical trials and the prediction of the efficacy of therapeutic drugs in patients. Furthermore, the analysis of iPSCs from clinical trial participants enables comparison of the results of clinical trials with the results of analysis of culture dishes. This paper introduces some examples of recent progress in drug discovery and development for neurodegenerative diseases using iPSCs.