A disposable safety lancet device employed in an automated and painless procedure includes an outer casing, an inner sleeve, a lancet assembly and a spring. A lancet tube is provided in the lancet assembly. One end of the lancet assembly is snapped in the inner sleeve, and the other end is extended into the outer casing. Interlock fixing faces and protrusions are provided on the inner sleeve. Interlock guiding slopes and protrusion stoppers are provided on the inner wall of the outer casing. One end of the interlock engages the interlock fixing face, and the other end engages the interlock guiding slope. A lancing operation for taking blood can be simply performed only by turning wing plates having rib portions, aligning a blood taking aperture, and pushing the outer casing. After the lancing operation, the lancet tip is retracted into the inner sleeve, which prevents a second use by the fixation between the inner sleeve and the outer casing. Additionally, the lancet device can control the depth of lancing operation.
