The present invention relates to a device for detecting a non-authorized material in a zone with protected access, the device being characterized by the fact that it comprises in combination: a supporting base (100) designed to receive a single foot wearing a shoe, of an individual to be inspected; detector means (430, 450, 460) adapted to detect a target material by employing at least one magnetic resonance technique to detect said non-authorized material and associated with the support base (100); and position-identifying means (400) on the support base (100) suitable for imposing accurate positioning of the foot of the individual being inspected relative to the detector means.