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 (L) 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 (A) 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 (L) 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 (A) 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 (L) 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 (A) between the inner peripheral cylindrical surface and the straight portion has an axial length shorter than an entire axial length of the straight portion . <EOS>