A position detection apparatus comprising: a magnetic flux detection means having one or more pairs of Hall sensors (32a, 32b), each pair comprised of two Hall sensors (32a, 32b), each Hall sensor (32, 32b) arranged on a substrate and having a magnetism sensing direction orthogonal to a substrate direction; and a rectangular solid magnet having an N-pole and an S-pole magnetized in a direction orthogonal to the substrate, wherein the rectangular solid magnet is arranged movably in a direction orthogonal to a line connecting the centers of magnetism sensing sections of the each pair of two Hall sensors (32a, 32b) and is arranged movably in a plane parallel to the substrate, wherein the rectangular solid magnet has a long side and a short side of a quadrangle when the rectangular solid magnet is projected on any plane parallel to the substrate; and wherein the magnetic flux detection means is configured such that the position detecting of the rectangular solid magnet is performed based on the relationship between the movement quantity of the rectangular solid magnet and a differential magnetic flux density represented as a difference between a magnetic flux density at the position of one hall sensor and a magnetic flux density at the position of the other hall sensor in the each pair of two hall sensors of the magnetic flux detection means, when the rectangular solid magnet is moved in a direction (x) orthogonal to a line connecting the centres of magnetism sensing sections of the each pair of two hall sensors in a state that the long side of the rectangular solid magnet has a predetermined inclination angle to the line connecting the centers of magnetism sensing sections of the each pair of two Hall sensors of the magnetic flux detection means. a magnetic flux detection means having one or more pairs of Hall sensors (32a, 32b), each pair comprised of two Hall sensors (32a, 32b), each Hall sensor (32, 32b) arranged on a substrate and having a magnetism sensing direction orthogonal to a substrate direction; and a rectangular solid magnet having an N-pole and an S-pole magnetized in a direction orthogonal to the substrate, wherein the rectangular solid magnet is arranged movably in a direction orthogonal to a line connecting the centers of magnetism sensing sections of the each pair of two Hall sensors (32a, 32b) and is arranged movably in a plane parallel to the substrate, wherein the rectangular solid magnet has a long side and a short side of a quadrangle when the rectangular solid magnet is projected on any plane parallel to the substrate; and wherein the magnetic flux detection means is configured such that the position detecting of the rectangular solid magnet is performed based on the relationship between the movement quantity of the rectangular solid magnet and a differential magnetic flux density represented as a difference between a magnetic flux density at the position of one hall sensor and a magnetic flux density at the position of the other hall sensor in the each pair of two hall sensors of the magnetic flux detection means, when the rectangular solid magnet is moved in a direction (x) orthogonal to a line connecting the centres of magnetism sensing sections of the each pair of two hall sensors in a state that the long side of the rectangular solid magnet has a predetermined inclination angle to the line connecting the centers of magnetism sensing sections of the each pair of two Hall sensors of the magnetic flux detection means.