A wearable-type artificial leg motion assisting apparatus (1, 70) provided separately from a trans-femoral prosthesis including a knee joint coupling for rotatably coupling a thigh socket for housing an above knee amputated end of a wearer to a lower leg support pole engaged with a foot part, the artificial leg motion assisting apparatus (1, 70) supporting a rotational motion of the knee joint coupling, the artificial leg motion assisting apparatus (1, 70) comprising: - a thigh frame (3, 72) fastened to the thigh socket via a fastening member; - a lower leg frame (4, 73) movably retained at the lower leg support pole via a holding member; - a drive unit (2, 71) that is coupled to the thigh frame (3, 72) and the lower leg frame (4, 73) and that is configured to drive actively or passively in conjunction with a thigh motion of the wearer; - a biological signal detection unit that is configured to detect an electrical potential as a biological signal generated in association with the thigh motion of the wearer; - a control unit that is configured to cause the drive unit (2, 71) to generate motive power according to an intention of the wearer on the basis of the biological signal acquired by the biological signal detection unit; - a coupling's physical amount detection unit (22, 23, 25) that is configured to detect a physical amount of the knee joint coupling in association with the thigh motion of the wearer on the basis of an output signal from the drive unit (2, 71); characterised in that it further comprises: - a leg motion monitoring unit (27, 28, 29) which is provided on the trans-femoral prosthesis and which is configured to monitor a motion of a leg part where the trans-femoral prosthesis is not mounted; - a parameter estimation unit that is configured to estimate a kinetic parameter specific to the trans-femoral prosthesis on the basis of a result of the detection measured within a specified amount of time by the coupling's physical amount detection unit (22, 23, 25) and a result of the monitoring by the leg motion monitoring unit (27, 28, 29); and - an impedance adjustment unit that is configured to adjust mechanical impedance specific to the knee joint coupling on the basis of the kinetic parameter estimated by the parameter estimation unit, wherein the control unit is configured to control the drive unit (2, 71) by a specified control method on the basis of the mechanical impedance adjusted by the impedance adjustment unit. - a thigh frame (3, 72) fastened to the thigh socket via a fastening member; - a lower leg frame (4, 73) movably retained at the lower leg support pole via a holding member; - a drive unit (2, 71) that is coupled to the thigh frame (3, 72) and the lower leg frame (4, 73) and that is configured to drive actively or passively in conjunction with a thigh motion of the wearer; - a biological signal detection unit that is configured to detect an electrical potential as a biological signal generated in association with the thigh motion of the wearer; - a control unit that is configured to cause the drive unit (2, 71) to generate motive power according to an intention of the wearer on the basis of the biological signal acquired by the biological signal detection unit; - a coupling's physical amount detection unit (22, 23, 25) that is configured to detect a physical amount of the knee joint coupling in association with the thigh motion of the wearer on the basis of an output signal from the drive unit (2, 71); - a leg motion monitoring unit (27, 28, 29) which is provided on the trans-femoral prosthesis and which is configured to monitor a motion of a leg part where the trans-femoral prosthesis is not mounted; - a parameter estimation unit that is configured to estimate a kinetic parameter specific to the trans-femoral prosthesis on the basis of a result of the detection measured within a specified amount of time by the coupling's physical amount detection unit (22, 23, 25) and a result of the monitoring by the leg motion monitoring unit (27, 28, 29); and - an impedance adjustment unit that is configured to adjust mechanical impedance specific to the knee joint coupling on the basis of the kinetic parameter estimated by the parameter estimation unit,