An overshoot amount detection method includes a first step of generating a first signal from a first detection signal output from an inertial sensor that detects inertia in a working unit of an arm to be displaced, a second step of generating a second signal using a second detection signal output from an encoder that detects an amount of displacement of the arm, and a third step of detecting an overshoot amount of the arm based on a third signal obtained by synthesis of the first signal and the second signal. The first step includes twice integration of the first detection signal and removing a low-frequency component contained in the first detection signal.