A medical manipulator (20A) includes: a holding portion (21A) whose proximal end portion (22A) is fixed to a base (16) a positioning portion (24A) that has a fixing portion (51A) that is fixed to a distal end portion (23A) of the holding portion, and that is formed such that a treatment portion (303) of a surgical instrument (200) is capable of moving relative to the fixing portion a reference orientation detecting portion (27A) that detects an orientation of a reference position on the positioning portion a drive section (28A) that is used to move the treatment portion relative to the fixing portion and a displacement detecting section that detects an amount of movement, including angular displacement, of the treatment portion relative to the reference position, and that calculates as the orientation on the treatment portion an orientation that is different by an amount of angular displacement which has detected by the displacement detecting section from the orientation on the reference position detected by the reference orientation detecting portion.
