A position detecting apparatus configured to detect a position of a magnet that moves in a direction of magnetization, the position detecting apparatus comprising: a first bridge circuit including: a magnetoresistive element having a maximum sensitivity to a magnetic field in a first direction the same as the direction of magnetization; and a magnetoresistive element having a maximum sensitivity to a magnetic field in a second direction perpendicular to the first direction, the first bridge circuit outputting a SIN signal; a second bridge circuit including: a magnetoresistive element having a maximum sensitivity to a third direction tilted against the first direction by 45 degrees; and a magnetoresistive element having a maximum sensitivity to a fourth direction perpendicular to the third direction, the second bridge circuit outputting a COS signal; area-identifying means having a magnetic-field direction-detecting sensor (26, 26a), and configured to output an area-identifying signal for identifying whether the magnet is in an area defined on one side from a center of the first bridge circuit and the second bridge circuit in a moving direction of the magnet, or in an area defined on the other side from the center of the first bridge circuit and the second bridge circuit in the moving direction of the magnet; the position detecting apparatus being characterised in that it further comprises: an ATAN2 value calculating unit configured to compute an ATAN2 value on the basis of the SIN signal and the COS signal; and a position-computing unit configured to compute a position of the magnet on the basis of the area-identifying signal and the ATAN2 value, wherein the position-computing unit is configured to compute a main area close to the center of the first bridge circuit and the second bridge circuit and a shift area (K1, K2) outside the main area, the ATAN2 value changing continuously in the main area, the shift area (K1, K2) being provided between a shift threshold (e, h) and a turn point (a, b) of the ATAN2 value, wherein the position-computing unit is configured to use the ATAN2 value ranges corresponding to the shift area (K1, K2) as an extension of the ATAN2 value range in the main area, so that the ATAN2 value can be obtained as a continuous value. a first bridge circuit including: a magnetoresistive element having a maximum sensitivity to a magnetic field in a first direction the same as the direction of magnetization; and a magnetoresistive element having a maximum sensitivity to a magnetic field in a second direction perpendicular to the first direction, the first bridge circuit outputting a SIN signal; a second bridge circuit including: a magnetoresistive element having a maximum sensitivity to a third direction tilted against the first direction by 45 degrees; and a magnetoresistive element having a maximum sensitivity to a fourth direction perpendicular to the third direction, the second bridge circuit outputting a COS signal; area-identifying means having a magnetic-field direction-detecting sensor (26, 26a), and configured to output an area-identifying signal for identifying whether the magnet is in an area defined on one side from a center of the first bridge circuit and the second bridge circuit in a moving direction of the magnet, or in an area defined on the other side from the center of the first bridge circuit and the second bridge circuit in the moving direction of the magnet; the position detecting apparatus being characterised in that it further comprises: an ATAN2 value calculating unit configured to compute an ATAN2 value on the basis of the SIN signal and the COS signal; and a position-computing unit configured to compute a position of the magnet on the basis of the area-identifying signal and the ATAN2 value, wherein the position-computing unit is configured to compute a main area close to the center of the first bridge circuit and the second bridge circuit and a shift area (K1, K2) outside the main area, the ATAN2 value changing continuously in the main area, the shift area (K1, K2) being provided between a shift threshold (e, h) and a turn point (a, b) of the ATAN2 value, wherein the position-computing unit is configured to use the ATAN2 value ranges corresponding to the shift area (K1, K2) as an extension of the ATAN2 value range in the main area, so that the ATAN2 value can be obtained as a continuous value. an ATAN2 value calculating unit configured to compute an ATAN2 value on the basis of the SIN signal and the COS signal; and a position-computing unit configured to compute a position of the magnet on the basis of the area-identifying signal and the ATAN2 value, wherein the position-computing unit is configured to compute a main area close to the center of the first bridge circuit and the second bridge circuit and a shift area (K1, K2) outside the main area, the ATAN2 value changing continuously in the main area, the shift area (K1, K2) being provided between a shift threshold (e, h) and a turn point (a, b) of the ATAN2 value,