A foil bearing, comprising: a foil holder; and a plurality of foils fixed to the foil holder so as to be arrayed in a circumferential direction of the foil bearing, each of the foils comprising: a top foil portion having a bearing surface; an extending portion formed on one circumferential side of the top foil portion; an underfoil portion formed on another circumferential side of the top foil portion and arranged between the top foil portion of another of the foils and the foil holder; and an insertion slot formed between the top foil portion and the underfoil portion in the circumferential direction, into which the extending portion of the another of the foils is inserted, the insertion slot comprising a positioning portion (12d1) to be engaged with the extending portion of the another of the foils in the circumferential direction, characterized in that the insertion slot further comprises: a wide portion (12d2) that is larger in circumferential width than the positioning portion (12d1) and is opened to an end portion of the each of the foils, wherein an edge (12e2) of the top foil portion, which faces to the wide portion (12d2) of the insertion slot, is retreated toward the one circumferential side with respect to an edge (12e1) of the top foil portion, which faces to the positioning portion (12d1) of the insertion slot. a foil holder; and a plurality of foils fixed to the foil holder so as to be arrayed in a circumferential direction of the foil bearing, each of the foils comprising: a top foil portion having a bearing surface; an extending portion formed on one circumferential side of the top foil portion; an underfoil portion formed on another circumferential side of the top foil portion and arranged between the top foil portion of another of the foils and the foil holder; and an insertion slot formed between the top foil portion and the underfoil portion in the circumferential direction, into which the extending portion of the another of the foils is inserted, the insertion slot comprising a positioning portion (12d1) to be engaged with the extending portion of the another of the foils in the circumferential direction, characterized in that a top foil portion having a bearing surface; an extending portion formed on one circumferential side of the top foil portion; an underfoil portion formed on another circumferential side of the top foil portion and arranged between the top foil portion of another of the foils and the foil holder; and an insertion slot formed between the top foil portion and the underfoil portion in the circumferential direction, into which the extending portion of the another of the foils is inserted, the insertion slot comprising a positioning portion (12d1) to be engaged with the extending portion of the another of the foils in the circumferential direction, characterized in that the insertion slot further comprises: a wide portion (12d2) that is larger in circumferential width than the positioning portion (12d1) and is opened to an end portion of the each of the foils, wherein an edge (12e2) of the top foil portion, which faces to the wide portion (12d2) of the insertion slot, is retreated toward the one circumferential side with respect to an edge (12e1) of the top foil portion, which faces to the positioning portion (12d1) of the insertion slot.