To provide a detection method and a detection device to detect a transition time of a control device which can measure the transition time with a high degree of precision.

The device for detecting a steady state behavior of a control device (4) comprises an absolute value generation unit (5) which generates a control deviation value (|e(t)|) of the control device, a first threshold detection unit (6) which detects whether the control deviation value (|e(t)|) of the control device is lower than the first threshold (Δa1) or not, and then starts a lag time delay unit (16), and a second threshold detection unit (11) which detects whether the control deviation value (|e(t)|) of the control device is lower than the second threshold (Δa2) or not. When the lag time delay unit (16) reaches a predetermined lag time (Tw) and the second threshold detection unit (11) detects that the control deviation value (|e(t)|) of the control device becomes lower than the second threshold (Δa2), a signal output unit (15) outputs a preparation completion notification signal (ALC_standby).