A medical support arm apparatus comprising: an arm section (510; 510a) including multiple joint sections (511a-f), and configured such that a medical tool is provided on a front end; an actuator provided at least in a compensated joint section (511d, 511e) that is a target of gravity compensation among the multiple joint sections, and including a torque sensor that detects a torque acting on the compensated joint section; a gravity compensation mechanism (540, 550; 540a, 550a) that imparts to the compensated joint section a compensating torque in a direction that causes the compensating torque to partly cancel out a load torque due to a self-weight of the arm section acting on the compensated joint section; wherein at least one further joint section (511a, 511b, 511c) among the multiple joint sections is located between the compensated joint section and the front end such that a length of a normal line extending from a center of rotation of the compensated joint section towards a vector indicating a direction of the gravitational force on the arm section varies non-monotonically with a rotational angle of the compensated joint section, the further joint section comprising an encoder; a control apparatus (530, 20) that at least controls a driving of the compensated joint section by causing the actuator to operate on a basis of at least a state of the compensated joint section detected by the torque sensor, wherein the control apparatus performs gravity compensation based on the compensating torque to cause the actuator to generate a torque based on a state of the at least one further joint section as detected by the encoder, that works, in combination with the compensating torque, to cancel out the load torque, the generated torque compensating for an insufficiency not fully compensated by the gravity compensation mechanism, the insufficiency being obtained by subtracting the compensating torque imparted to the compensating joint section by the gravity compensation mechanism from the load torque due to the self-weight of the arm section acting on the compensated joint section. an arm section (510; 510a) including multiple joint sections (511a-f), and configured such that a medical tool is provided on a front end; an actuator provided at least in a compensated joint section (511d, 511e) that is a target of gravity compensation among the multiple joint sections, and including a torque sensor that detects a torque acting on the compensated joint section; a gravity compensation mechanism (540, 550; 540a, 550a) that imparts to the compensated joint section a compensating torque in a direction that causes the compensating torque to partly cancel out a load torque due to a self-weight of the arm section acting on the compensated joint section; wherein at least one further joint section (511a, 511b, 511c) among the multiple joint sections is located between the compensated joint section and the front end such that a length of a normal line extending from a center of rotation of the compensated joint section towards a vector indicating a direction of the gravitational force on the arm section varies non-monotonically with a rotational angle of the compensated joint section, the further joint section comprising an encoder; a control apparatus (530, 20) that at least controls a driving of the compensated joint section by causing the actuator to operate on a basis of at least a state of the compensated joint section detected by the torque sensor, wherein the control apparatus performs gravity compensation based on the compensating torque to cause the actuator to generate a torque based on a state of the at least one further joint section as detected by the encoder, that works, in combination with the compensating torque, to cancel out the load torque, the generated torque compensating for an insufficiency not fully compensated by the gravity compensation mechanism, the insufficiency being obtained by subtracting the compensating torque imparted to the compensating joint section by the gravity compensation mechanism from the load torque due to the self-weight of the arm section acting on the compensated joint section.