We have developed a near-field optical probe by introducing the metallized pyramidal structure of a Si probe with a slit-shaped tip for high-density optical storage. Numerical analysis using the finite-difference time-domain method showed that the optical spot generated at the aperture measured 13×30 nm. We fabricated a slit-type Si probe and evaluated the spot size using fluorescence imaging of a single dye molecule. The full-width at half maximum of the signal profiles was 16 nm×26 nm, which corresponds to a data density of 1.5 Tbit/in2. Furthermore, a large extinction coefficient depending on the polarization was confirmed.