A variable PID gain design device, including: a parameter setting unit for setting a natural frequency, a damping ratio, a sampling time, and a nonlinear damping, which enable establishment of an error dynamics required for controlling an object to be controlled; a PID gain induction unit for inducing a PID gain, using the correlation between a PID control and a backstepping control with time delay estimation and nonlinear damping (BCTND), the PID control controlling, using the set parameters, the object to be controlled; and a PID gain calculating unit for calculating a gain of a PID controller by adjusting a BCTND control gain on the basis of the induced PID gain.
