An angular transmission error identification system that is configured to identify an angular transmission error of a speed reducer of a robot arm including a joint that is rotationally driven by a motor via the speed reducer, the angular transmission error identification system comprising an identification unit that is configured to calculate an amplitude parameter and a phase parameter of an angular transmission error identification function, which is a periodic function that models an angular transmission error of the speed reducer and has the amplitude parameter and the phase parameter, and configured to identify the angular transmission error using the angular transmission error identification function, characterised in that the identification unit is configured to perform the following calculations: when a gravitational torque current value, which is a gravitational torque value acting on the joint when the angular transmission error of the speed reducer is identified, is included in a predetermined numerical range which is a negative numerical range, the identification unit calculates the amplitude parameter corresponding to the gravitational torque current value using a first amplitude function that represents a correlation between the amplitude parameter and the gravitational torque value acting on the joint in a motion range in which the gravitational torque value acting on the joint takes a negative value in a motion range of the joint, when the gravitational torque current value is included in the predetermined numerical range which is the negative numerical range, the identification unit calculates the phase parameter corresponding to the gravitational torque current value using a first phase function that represents the correlation between the phase parameter and the gravitational torque value acting on the joint in the motion range in which the gravitational torque value acting on the joint takes a negative value in the motion range of the joint, when the gravitational torque current value is included in a predetermined numerical range which is a positive numerical range, the identification unit calculates the amplitude parameter corresponding to the gravitational torque current value using a second amplitude function that represents a correlation between the amplitude parameter and the gravitational torque value acting on the joint in a motion range in which the gravitational torque value acting on the joint takes a positive value in the motion range of the joint, and when the gravitational torque current value is included in the predetermined numerical range which is the positive numerical range, the identification unit calculates the phase parameter corresponding to the gravitational torque current value using a second phase function that represents the correlation between the phase parameter and the gravitational torque value acting on the joint in the motion range in which the gravitational torque value acting on the joint takes a positive value in the motion range of the joint. when a gravitational torque current value, which is a gravitational torque value acting on the joint when the angular transmission error of the speed reducer is identified, is included in a predetermined numerical range which is a negative numerical range, the identification unit calculates the amplitude parameter corresponding to the gravitational torque current value using a first amplitude function that represents a correlation between the amplitude parameter and the gravitational torque value acting on the joint in a motion range in which the gravitational torque value acting on the joint takes a negative value in a motion range of the joint, when the gravitational torque current value is included in the predetermined numerical range which is the negative numerical range, the identification unit calculates the phase parameter corresponding to the gravitational torque current value using a first phase function that represents the correlation between the phase parameter and the gravitational torque value acting on the joint in the motion range in which the gravitational torque value acting on the joint takes a negative value in the motion range of the joint, when the gravitational torque current value is included in a predetermined numerical range which is a positive numerical range, the identification unit calculates the amplitude parameter corresponding to the gravitational torque current value using a second amplitude function that represents a correlation between the amplitude parameter and the gravitational torque value acting on the joint in a motion range in which the gravitational torque value acting on the joint takes a positive value in the motion range of the joint, and when the gravitational torque current value is included in the predetermined numerical range which is the positive numerical range, the identification unit calculates the phase parameter corresponding to the gravitational torque current value using a second phase function that represents the correlation between the phase parameter and the gravitational torque value acting on the joint in the motion range in which the gravitational torque value acting on the joint takes a positive value in the motion range of the joint.