A medical diagnostic apparatus according to an embodiment includes a contact component, a deep ultraviolet source, and a processing circuitry. The contact component has a contact region that is contacted by a subject during a medical practice. The deep ultraviolet source is provided with the contact component to irradiate the contact region with deep ultraviolet rays. The processing circuitry is configured to control the deep ultraviolet source to irradiate the contact region with deep ultraviolet rays when the medical practice is not performed.