The early detection of diseases is key to improve the survival rate of patients. However, the most widely-used and well-developed biosensors for medical diagnostics, such as enzyme-linked immunosorbent assay (ELISA), have limitations when used for the early detection of diseases because (1) they are often expensive, (2) they require large reagents and sample volumes, and (3) they are operated only by trained personnel due to their complex operation procedures. A point-of-care (POC) biosensor has emerged as a promising technology for this purpose. Our group has proposed an optical cavity-based biosensor as a POC biosensor for the early detection of diseases. In this presentation, I will discuss the details of our optical cavity-based biosensor design and characteristics, and also the most recent progresses toward demonstrating its sensitivity and capability.