This metal detecting device is provided with: a detecting circuit unit (30) which executes a detection process of a first fluctuating component of a magnetic field fluctuating signal from a magnetic field receiving unit (23), the first fluctuating component having a large workpiece influence, and a second fluctuating component thereof having a large metal influence; a determining unit (40) which executes a metal detection determination process in a workpiece (W) by comparing the two fluctuating components; and a detection condition adjusting unit (60) which adjusts detection conditions of the two fluctuating components. The metal detecting device is provided with a foreign body waveform storage unit (50) in which is stored a test fluctuating component which accompanies a variation over time due to a metal influence. The detection condition adjusting unit (60) sets specific processing conditions for the detection process performed by the detecting circuit unit (30), on the basis of the first fluctuating compon
