Abstract: A blood vessel puncturing device includes an ultrasound sensor which is brought into close contact with a subject body via an ultrasound propagation medium in the form of gel. The ultrasound sensor transmits and receives an ultrasound wave. The device further includes a processor which processes a signal derived from the ultrasound wave received at the ultrasound sensor so as to display an image of the subject body including a superficial blood vessel. While watching the displayed image, an operator sticks a puncturing needle at an angle of not greater than 30 degrees relative to the subject body along an ultrasound scanning surface of the ultrasound sensor and inserts the tip of the puncturing needle into the blood vessel.