Abstract: The present invention relates to a support arm apparatus for supporting a medical instrument including: a support arm (1) having a first end, a second end, and a chamber extending from the first end to the second end, the support arm defining a longitudinal axis (x); a support part (2) arranged at the second end of the support arm (1); a ball joint (3) arranged at the first end of the support arm (1) and including a ball head (4) and a ball seat (5); a connecting component (6) connected to the ball head (4) and configured for connection with a medical instrument (10); and a locking device (30) including an operation element (11) and a locking element (12) movably arranged in the chamber and operable by the operation element in a direction in which the ball head is locked by the locking element. The support arm apparatus enables the medical instrument to be flexibly adjusted in position and orientation.