Abstract: A blood sampling device has a vacuum tube and a sleeve provided with a two-ended needle. When one end of the needle is placed in a vein in order to take a blood sample, a seal in the vacuum tube is perforated by the second end of the needle so as to create suction for taking a blood sample. The sleeve comprises a base with an outlet and guide aperture, and a tubular section for guiding and protecting the first end of the needle. The sleeve includes a guiding and locking groove with two locking positions. The locking positions consist of a longitudinal section corresponding substantially to the movement which the needle has to perform in order to pass from its retracted position into its operating position and terminating at each end in a locking extension which is transverse relative to the sliding direction and which corresponds to each of the two locking positions.