Positioning device, with a housing and at least one electromagnetic linear actuator, which comprises - an armature unit that can be moved relative to the housing, and which comprises a permanent magnet arrangement and a plunger coupled thereto, and which comprises - a coil arrangement (4, 4', 4") fixed to the housing and extending around the permanent magnet arrangement, and having at least one coil winding, wherein - the permanent magnet arrangement comprises an axially magnetised disc magnet and two flux guide pieces (11, 12) arranged on the end face thereof, - the disc magnet has a circular cylindrical outer surface, and the flux guide pieces (11, 12) are designed as circular flux guide discs, and wherein the coil arrangement (4, 4', 4") has a non-circular cross-section, at least in the region of its axial overlap with the permanent magnet arrangement, characterised in that, - the inner surface of the coil arrangement has a gap (34, 34', 34") with a first clear radial dimension on at least two first circumferential sections (29, 29', 29") relative to the outer surface of the permanent magnet arrangement and a second clear radial dimension, which is enlarged relative to the first clear radial dimension, on at least two bulged-out second circumferential sections (30, 30', 30"), which are each associated with a bulge of the coil winding, to the outer surface of the permanent magnet arrangement with a second clear radial dimension, which is enlarged in comparison with the first clear radial dimension, wherein the maximum value of the second clear radial dimension is substantially greater than that of the first clear radial dimension, - in the region of the at least two second circumferential sections (29, 29', 29"), between the permanent magnet arrangement and the coil arrangement (4, 4', 4"), there exists in each case a compensating channel (35, 35', 35") with a crescent-shaped cross-section. - an armature unit that can be moved relative to the housing, and which comprises a permanent magnet arrangement and a plunger coupled thereto, and which comprises - a coil arrangement (4, 4', 4") fixed to the housing and extending around the permanent magnet arrangement, and having at least one coil winding, wherein - the permanent magnet arrangement comprises an axially magnetised disc magnet and two flux guide pieces (11, 12) arranged on the end face thereof, - the disc magnet has a circular cylindrical outer surface, and the flux guide pieces (11, 12) are designed as circular flux guide discs, and wherein the coil arrangement (4, 4', 4") has a non-circular cross-section, at least in the region of its axial overlap with the permanent magnet arrangement, characterised in that, - the inner surface of the coil arrangement has a gap (34, 34', 34") with a first clear radial dimension on at least two first circumferential sections (29, 29', 29") relative to the outer surface of the permanent magnet arrangement and a second clear radial dimension, which is enlarged relative to the first clear radial dimension, on at least two bulged-out second circumferential sections (30, 30', 30"), which are each associated with a bulge of the coil winding, to the outer surface of the permanent magnet arrangement with a second clear radial dimension, which is enlarged in comparison with the first clear radial dimension, wherein the maximum value of the second clear radial dimension is substantially greater than that of the first clear radial dimension, - in the region of the at least two second circumferential sections (29, 29', 29"), between the permanent magnet arrangement and the coil arrangement (4, 4', 4"), there exists in each case a compensating channel (35, 35', 35") with a crescent-shaped cross-section.