A position detecting device comprising: a scale including a magnetic medium having a magnetic signal with a constant period magnetically recorded thereon; a plurality of magnetism detecting elements each configured to detect a leakage magnetism from the magnetic signal of the scale and output a signal corresponding to the magnetic signal at a position where the leakage magnetism has been detected; and a position detecting section configured to detect a position relative to the scale based on each output signal corresponding to the magnetic signal, wherein the plurality of magnetism detecting elements are formed into a plurality of groups of magnetism detecting elements, from which at least one set of signals, having phases different from each other, are output, the plurality of groups of magnetism detecting elements are arranged, in a detection direction of the magnetic signal relative to the scale, at positions each being shifted relative to one of the groups in the detection direction such that phases of respective output signals of the plurality of groups are each shifted relative to one of the groups by a range shorter than one unit wavelength of the magnetic signal, each of the plurality of groups comprising plural magnetism detecting elements, the plural magnetism detecting elements of each of the plurality of groups being arranged along the detection direction of the magnetic signal relative to the scale, and the plurality of groups of magnetism detecting elements being spaced from each other in a direction orthogonal to the detection direction, within a range shorter than one unit wavelength of the magnetic signal. a scale including a magnetic medium having a magnetic signal with a constant period magnetically recorded thereon; a plurality of magnetism detecting elements each configured to detect a leakage magnetism from the magnetic signal of the scale and output a signal corresponding to the magnetic signal at a position where the leakage magnetism has been detected; and a position detecting section configured to detect a position relative to the scale based on each output signal corresponding to the magnetic signal, wherein the plurality of magnetism detecting elements are formed into a plurality of groups of magnetism detecting elements, from which at least one set of signals, having phases different from each other, are output, the plurality of groups of magnetism detecting elements are arranged, in a detection direction of the magnetic signal relative to the scale, at positions each being shifted relative to one of the groups in the detection direction such that phases of respective output signals of the plurality of groups are each shifted relative to one of the groups by a range shorter than one unit wavelength of the magnetic signal, each of the plurality of groups comprising plural magnetism detecting elements, the plural magnetism detecting elements of each of the plurality of groups being arranged along the detection direction of the magnetic signal relative to the scale, and the plurality of groups of magnetism detecting elements being spaced from each other in a direction orthogonal to the detection direction, within a range shorter than one unit wavelength of the magnetic signal.