1. A method of detecting a position of an alignment mark on an object including a mark element, said method comprising the steps of: obtaining a signal waveform of the mark element with a position detector; extracting at least two kinds of waveform feature values from the signal waveform of the mark element, by using extracting methods different from each other, each of the at least two kinds of waveform feature values being a parameter that characterizes the signal waveform of the mark element; detecting a real position of the mark element by signal processing; and correcting the real position based on the at least two kinds of waveform feature values and a function that correlates the at least two kinds of waveform feature values and a shift amount between a true value indicating an ideal position of the mark element and the real position of the mark element, wherein one of the at least two kinds of waveform feature values is a difference between two detection results of the mark element that are respectively detected by two signal processings different from each other.