An air foil journal bearing comprising: a bearing housing having a through hole in which a rotor is disposed; a bump foil disposed inside the bearing housing and formed in a circumferential direction thereof, having an uneven-shaped elastic bump, having one end coupled and fixed to the bearing housing in the circumferential direction, and having the other end formed as a free end in the circumferential direction; an outer top foil disposed inside the bump foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction; an inner top foil disposed inside the outer top foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction; and a middle top foil interposed between the outer top foil and the inner top foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction, wherein the outer top foil and the inner top foil each have a fixed tab (330, 530) formed by extending from a portion between both sides of the other end in the circumferential direction of the foil in a width direction thereof, and the outer top foil, the middle top foil and the inner top foil each have a through hole (340, 440, 540) formed at one side thereof in the circumferential direction, the through hole (340, 440, 540) passing through the inside and outside of the foil at a position corresponding to a position of the fixed tab of the inner top foil, the free end of the bump foil has a through hole passing through the inside and outside of the foil at a position corresponding to a position of the fixed tab (330, 530) formed between both sides of the free end in the width direction, and the outer top foil and the inner top foil are each rolled in one or more turns, and the fixed tabs (330, 530) of the outer top foil and inner top foil are each inserted through and disposed in the through holes (240, 340, 440, 540) of the inner top foil, the middle top foil, the outer top foil and the bump foil. a bearing housing having a through hole in which a rotor is disposed; a bump foil disposed inside the bearing housing and formed in a circumferential direction thereof, having an uneven-shaped elastic bump, having one end coupled and fixed to the bearing housing in the circumferential direction, and having the other end formed as a free end in the circumferential direction; an outer top foil disposed inside the bump foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction; an inner top foil disposed inside the outer top foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction; and a middle top foil interposed between the outer top foil and the inner top foil, formed in the circumferential direction, and having one end coupled and fixed to the bearing housing in the circumferential direction, wherein the outer top foil and the inner top foil each have a fixed tab (330, 530) formed by extending from a portion between both sides of the other end in the circumferential direction of the foil in a width direction thereof, and the outer top foil, the middle top foil and the inner top foil each have a through hole (340, 440, 540) formed at one side thereof in the circumferential direction, the through hole (340, 440, 540) passing through the inside and outside of the foil at a position corresponding to a position of the fixed tab of the inner top foil, the free end of the bump foil has a through hole passing through the inside and outside of the foil at a position corresponding to a position of the fixed tab (330, 530) formed between both sides of the free end in the width direction, and the outer top foil and the inner top foil are each rolled in one or more turns, and the fixed tabs (330, 530) of the outer top foil and inner top foil are each inserted through and disposed in the through holes (240, 340, 440, 540) of the inner top foil, the middle top foil, the outer top foil and the bump foil.