A micro-needle array was fabricated on a polycarbonate (PC) substrate using an electroformed-Ni mold with a conical concave pattern. The diameter and length of each needle were 50 μm and 135 μm, respectively. The needle array pattern of the electroformed-Ni mold was produced by combining a grayscale mask for X-ray lithography with Ni electroforming technology. The X-ray grayscale mask was composed of Si absorbers and a SU-8 membrane. Each Si absorber had a three-dimensional cone shape rather than a rectangular shape. Threedimensional Si structures were formed to etch an active Si layer in a silicon-on-insulator wafer using a taperedtrench etching technology. Beamline BL-4 in the TERAS synchrotron radiation facility at AIST was used for the Xray lithography experiments. X-rays that penetrated the X-ray grayscale mask irradiated a polymethylmethacrylate (PMMA) sheet. Pt was deposited on the PMMA structure after developing, and Ni was electroformed on it. The electroformed-Ni object was processed by grinding to complete a Ni mold. Finally, the micro-needle array was fabricated by thermal-imprinting on a 0.5-mm thick PC sheet with the electroformed Ni mold.