A biopsy tissue sampling treatment instrument comprising: a tissue sampling unit having a predetermined length sufficient to puncture living tissue; a puncturing portion formed at a distal end of the tissue sampling unit and having a protruding surface portion expanding in a rearward direction along a puncture direction of the tissue sampling unit; a first tissue holding surface provided on a rear side of the protruding surface portion in the puncturing portion and having an area large enough to hold the living tissue; a protruding portion provided on a stem portion of the tissue sampling unit and extending in a diameter direction of the stem portion, the protruding portion including a second tissue holding surface (14a, 21a) formed toward the rearward direction and having an area large enough to hold the living tissue; characterised in that the instrument further comprises a stopper member provided at a rear end of the tissue sampling unit so as to be separated from a distal end of the puncturing portion by a distance corresponding to a depth at which the living tissue is extracted, the stopper member having an abutting portion capable of abutting against the living tissue when the tissue sampling unit is punctured into the living tissue, thereby allowing to extract the living tissue at the depth at which the stopper member is separated from the distal end of the puncturing portion; and an operating member fixedly fitted to an insertion member fitted to the stopper member and configured to hold the tissue sampling unit, allowing the tissue sampling unit to puncture the living tissue, the stopper member being larger in an external dimension around the longitudinal axis of the stem portion than are the puncturing portion and the first tissue holding surface, the operating member being connected to a rear end of the insertion member which has flexibility and which extends from a rear end of the stem portion, and the operating member being disposed at a rear end of the insertion member and holds the stem portion through the insertion member, allowing the stem portion to puncture the living tissue. a tissue sampling unit having a predetermined length sufficient to puncture living tissue; a puncturing portion formed at a distal end of the tissue sampling unit and having a protruding surface portion expanding in a rearward direction along a puncture direction of the tissue sampling unit; a first tissue holding surface provided on a rear side of the protruding surface portion in the puncturing portion and having an area large enough to hold the living tissue; a protruding portion provided on a stem portion of the tissue sampling unit and extending in a diameter direction of the stem portion, the protruding portion including a second tissue holding surface (14a, 21a) formed toward the rearward direction and having an area large enough to hold the living tissue; characterised in that the instrument further comprises a stopper member provided at a rear end of the tissue sampling unit so as to be separated from a distal end of the puncturing portion by a distance corresponding to a depth at which the living tissue is extracted, the stopper member having an abutting portion capable of abutting against the living tissue when the tissue sampling unit is punctured into the living tissue, thereby allowing to extract the living tissue at the depth at which the stopper member is separated from the distal end of the puncturing portion; and an operating member fixedly fitted to an insertion member fitted to the stopper member and configured to hold the tissue sampling unit, allowing the tissue sampling unit to puncture the living tissue, the stopper member being larger in an external dimension around the longitudinal axis of the stem portion than are the puncturing portion and the first tissue holding surface, the operating member being connected to a rear end of the insertion member which has flexibility and which extends from a rear end of the stem portion, and the operating member being disposed at a rear end of the insertion member and holds the stem portion through the insertion member, allowing the stem portion to puncture the living tissue.