Abstract: A puncturing needle device for introducing a catheter into a blood vessel, including a body; a catheter duct passing through the body for guiding a catheter therethrough; a syringe duct extending in the body from a syringe duct opening provided in the body and merging into the catheter duct at a merging location between opposite ends thereof for receiving a syringe introducible into the syringe duct through the syringe duct opening; and a needle having a throughgoing inner passage and an end attached to the body to communicate with the catheter duct. The inner wall surface of the catheter duct and the inner wall surface of the needle passage form a smooth transition from the catheter duct to the passage. The syringe duct and the passage are oriented to one another at an oblique angle. There is further provided a lock element positioned in the catheter duct between the merging location and that end of the catheter duct which is distal from the needle passage.