A magnetic tunnel element (1) including a plurality of ferromagnetic films (5, 9) laminated across an insulating film (11) formed of metal oxide films (6, 7, 8) and in which asymmetric tunnel barriers are formed along the direction in which the ferromagnetic films (5, 9) are laminated by this insulating film (11) (6, 7, 8). There are also constructed a thin-film magnetic head, a magnetic memory and a magnetic sensor, each of which includes the magnetic tunnel element (1). Since a magnetoresistive ratio can be suppressed from being lowered by decreasing a bias voltage dependency, there are provided a highly-reliable magnetic tunnel element which can obtain a high output when the magnetic tunnel element is applied to a thin-film magnetic head and the like and a method of manufacturing such a magnetic tunnel element. When a magnetic head, a magnetic memory and a magnetic sensor include this magnetic tunnel element, they become highly reliable and also become able to obtain a high output.