An insulated bearing device comprising: a housing formed with a housing hole; an outer ring fitted in the housing hole; an inner ring arranged radially inwardly of, and coaxially with, the outer ring; and a plurality of rolling elements disposed between the outer ring and the inner ring, wherein an insulating film that provides electrical insulation between the housing and the outer ring is disposed on a surface of the outer ring, wherein the insulating film comprises: a straight portion extending along an outer periphery of the outer ring and having a constant outer diameter in an axial direction; a pair of end surface portions extending along respective end surfaces of the outer ring on both axial sides of the outer ring; and a pair of chamfers having a circular arc-shaped cross section, and connecting together the straight portion and the respective end surface portions, wherein the housing has, on an inner periphery of the housing hole, an inner peripheral cylindrical surface formed at a position intersecting with axial centerlines of the rolling elements, and the straight portion is fitted to and in contact with the inner peripheral cylindrical surface, the insulated bearing device characterised in that a contact area between the inner peripheral cylindrical surface and the straight portion has an axial length shorter than an entire axial length of the straight portion. a housing formed with a housing hole; an outer ring fitted in the housing hole; an inner ring arranged radially inwardly of, and coaxially with, the outer ring; and a plurality of rolling elements disposed between the outer ring and the inner ring, wherein an insulating film that provides electrical insulation between the housing and the outer ring is disposed on a surface of the outer ring, wherein the insulating film comprises: a straight portion extending along an outer periphery of the outer ring and having a constant outer diameter in an axial direction; a pair of end surface portions extending along respective end surfaces of the outer ring on both axial sides of the outer ring; and a pair of chamfers having a circular arc-shaped cross section, and connecting together the straight portion and the respective end surface portions, wherein the housing has, on an inner periphery of the housing hole, an inner peripheral cylindrical surface formed at a position intersecting with axial centerlines of the rolling elements, and the straight portion is fitted to and in contact with the inner peripheral cylindrical surface, the insulated bearing device characterised in that a contact area between the inner peripheral cylindrical surface and the straight portion has an axial length shorter than an entire axial length of the straight portion. a straight portion extending along an outer periphery of the outer ring and having a constant outer diameter in an axial direction; a pair of end surface portions extending along respective end surfaces of the outer ring on both axial sides of the outer ring; and a pair of chamfers having a circular arc-shaped cross section, and connecting together the straight portion and the respective end surface portions, wherein the housing has, on an inner periphery of the housing hole, an inner peripheral cylindrical surface formed at a position intersecting with axial centerlines of the rolling elements, and the straight portion is fitted to and in contact with the inner peripheral cylindrical surface, the insulated bearing device characterised in that a contact area between the inner peripheral cylindrical surface and the straight portion has an axial length shorter than an entire axial length of the straight portion.