A medical supporting arm according to the present disclosure includes a supporting arm and a calculation unit. The supporting arm supports an oblique-viewing endoscope. The calculation unit calculates a rotation angle of the oblique-viewing endoscope around an axis in a longitudinal direction, and an insertion amount of the oblique-viewing endoscope into a human body on the basis of a first expression that defines coordinates of a subject in a coordinate system in which an insertion opening allowing the oblique-viewing endo scope to be inserted into the human body serves as an origin, and a second expression that defines the coordinates of the subject positioned in an optical axis direction of an objective lens disposed at a distal end of the oblique-viewing endoscope in a coordinate system in which the distal end of the oblique-viewing endoscope serves as an origin.