Clostridioides difficile (C. difficile) colitis and pseudomembranous colitis are known as healthcare-associated intestinal infections. In this study, the incidence of C. difficile colitis and pseudomembranous colitis was investigated using the Japanese Adverse Drug Event Report (JADER). Using JADER data between April 2004 and September 2017, the patient who developed C. difficile colitis and pseudomembranous colitis were investigated. During the study period, 375 cases of C. difficile colitis and 903 cases of pseudomembranous colitis were reported. The numbers of reported cases of both C. difficile colitis and pseudomembranous colitis were largest in those in their 70s, accounting for 24.7% and 25.6%, respectively. Patients in their 60s-90s comprised the majority of all patients with both C. difficile colitis and pseudomembranous colitis. Both C. difficile colitis and pseudomembranous colitis were caused by antibiotics in many patients, and signals of all antibiotics were detected. In C. difficile colitis, signals of immunosuppressants, corticosteroids, and alkylating drugs were also detected among drugs other than antibiotics. For pseudomembranous colitis, the use of molecularly targeted drugs, antimetabolic drugs, and corticosteroids was reported other than antibiotics. Using JADER, we revealed risk factors for the development of C. difficile colitis and pseudomembranous colitis, and firstly revealed that molecularly targeted drugs other than antibiotics could also be potential risk factors. Our findings may be useful for the early detection of drug-induced C. difficile colitis and pseudomembranous colitis.