The present invention relates to a device for positioning and/or orienting, in the body of a patient, a surgical tool (10) carried by a tool-holder (8), comprising: - a platform (1) capable of being placed on the body of the patient, - an orientable carrier (9), at least one part of which is rigidly connected to the tool-holder (8), - means (6, 7, 20, 23) for guiding the orientable carrier (9) rotationally relative to the platform (1) in two directions (a1, a2) of a plane parallel to the platform (1), - at least 2 pneumatic actuators (11, 12; 11A, 11B, 11C) which engage with said orientable carrier (9) such that a variation in pressure of at least one of the pneumatic actuators causes the orientable carrier (9) to rotate in the first direction (a1) and/or the second direction (a2), in which said pneumatic actuators (11, 12) are volumes that can deform in a predetermined direction as a function of the internal pressure.