A detecting apparatus includes a target section in which target elements to be detected are arranged in the direction of the motion of a moving body; a detecting section that detects the target elements with the motion of the moving body and outputs a waveform signal having an output level corresponding to its detection sensitivity; a first-digital-signal output section that binarizes the waveform signal with reference to a first threshold to output a first digital signal; a second-digital-signal output section that binarizes the waveform signal with reference to a second threshold which is higher in absolute value than the first threshold to output a second digital signal; and a determining section that determines whether the second digital signal has changed in status.