A hollow optical fiber (HOF) Roman probe equipped with a ball lens is developed to study the stomach cancer. The probe generates little Raman scattering or fluorescence noise because the HOF confine light into the air core. In order to maximize the collection efficiency and the spatial resolution, material and size of the ball lens is optimized. The total diameter of the probe head is 640 μm. The probe is useful for measurement of layered sample by the contact mode because it has very short focal length and high depth resolution. In vivo experiments in a stomach of a living rat demonstrate the high viability of the probe for noninvasive diagnosis of the stomach cancer.