A medical robot comprising: a bed on which an object is to be disposed; and a robot arm unit disposed above or below the bed, and comprising an emitting member movable within a trajectory on a sphere having a center at which a target point is disposed, wherein the bed and the robot arm unit can move relatively in a vertical or horizontal direction, and the object is repositioned to the target point by relatively moving the bed and the robot arm unit in the vertical or horizontal direction, and the emitting member moves to face the target point, characterized in that the robot arm unit comprises: a first central member; a first link member to rotate on a longitudinal axis (X A) of the first central member; a second link member connected to another end of the first link member to rotate on a first axis (X 1); a third link member connected to a portion of the first central member, the portion differing from a portion to which the first link member is connected, to rotate on the longitudinal axis of the first central member, and a fourth link member connected to another end of the third link member to rotate on a second axis (X 2); wherein respective end portions of the second link member and the fourth link member are provided with the emitting member, wherein the first link member, the second link member, the third link member and the fourth link member are provided in form of an arc, and the first link member and the third link member may rotate in different directions or at different velocities. a bed on which an object is to be disposed; and a robot arm unit disposed above or below the bed, and comprising an emitting member movable within a trajectory on a sphere having a center at which a target point is disposed, wherein the bed and the robot arm unit can move relatively in a vertical or horizontal direction, and the object is repositioned to the target point by relatively moving the bed and the robot arm unit in the vertical or horizontal direction, and the emitting member moves to face the target point, characterized in that the robot arm unit comprises: a first central member; a first link member to rotate on a longitudinal axis (X A) of the first central member; a second link member connected to another end of the first link member to rotate on a first axis (X 1); a third link member connected to a portion of the first central member, the portion differing from a portion to which the first link member is connected, to rotate on the longitudinal axis of the first central member, and a fourth link member connected to another end of the third link member to rotate on a second axis (X 2); wherein respective end portions of the second link member and the fourth link member are provided with the emitting member, wherein the first link member, the second link member, the third link member and the fourth link member are provided in form of an arc, and the first link member and the third link member may rotate in different directions or at different velocities. a first central member; a first link member to rotate on a longitudinal axis (X A) of the first central member; a second link member connected to another end of the first link member to rotate on a first axis (X 1); a third link member connected to a portion of the first central member, the portion differing from a portion to which the first link member is connected, to rotate on the longitudinal axis of the first central member, and a fourth link member connected to another end of the third link member to rotate on a second axis (X 2); wherein respective end portions of the second link member and the fourth link member are provided with the emitting member, wherein the first link member, the second link member, the third link member and the fourth link member are provided in form of an arc, and the first link member and the third link member may rotate in different directions or at different velocities.