The dielectric functions of direct-current-sputtered wedge-shaped ultrathin titanium (Ti) film on K9 glass were investigated in this paper. The wedge-shaped Ti thin film was deposited under the identical conditions with continuously varied thickness. Atomic force microscope revealed that the thin film surface was very smooth with the surface roughness of about 0.5 nm. The dielectric functions of the wedge-shaped films in the wavelength range of 300–1200 nm were obtained by a focused-beam ellipsometer with the beam size on the sample about 200 μm. Results show that ε ₁, the real part of the dielectric function, is negative almost in the whole spectrum region, proving that the film at the measured area is continuous and shows metallic behavior. On the other hand, ε ₁ decreases with the increase in the film thickness, while ε ₂, the imaginary part of the dielectric function, has the opposite variation tendency. The changing of ε ₁ with film thickness is due to the reduced electron–electron interactions and enhanced metallic behavior. While for ε ₂, it gets larger with the increase in the film thickness, which is mainly owing to the decrease in the tensile stress in the film.