A needle tube includes: a tubular main body section; a distal opening section; a needle tip; a side hole disposed closer to the proximal end side of the main body than the tip; a side hole inner circumferential edge extending around the longitudinal axis of the main body where the side hole and the inner circumferential surface intersect; a side hole outer circumferential edge extending around the longitudinal axis of the main body where the side hole and the outer circumferential surface intersect; and an engaged surface formed between the side hole inner circumferential edge and the side hole outer circumferential edge to be directed toward the proximal end of the main body section and configured to lock biological tissue entering from the distal opening section, wherein the side hole forms an opening area smaller than that of the distal opening.