This medical treatment tool (1) includes: an end effector (10) which has a first forceps piece (11) and a second forceps piece (12) of which at least one is supported so that it is capable of being rotated relative to a cover member an operating member (20) which is configured to advance or retract in its own axial direction relative to the cover member so that the pair of forceps pieces rotates and opens/closes and a link member (15, 17) whose distal end portion (15A, 17A) is coupled to a rotatable forceps piece, and whose proximal end portion (15B, 17B) is coupled to the operating member wherein a drive axis of the proximal end portion (15B, 17B) is parallel with an axis of the operating member (20) the distance between the distal end portion (15A, 17A) and the drive axis of the proximal end portion (15B, 17B) is shorter than the length of the link member and the length (L1) of projection on the drive axis of a line segment which connects the second end portion and a center of rotation of the pair of the first forceps piece (11) and the second forceps piece (12) is shorter than the length (L2) of projection on the drive axis of a line segment which connects the distal end portion (15A, 17A) and the center of rotation.
