A bearing fixing device, comprising: at least one bearing having an inner ring and an outer ring that are mutually rotatable; a housing having at least one fitting hole into which the bearing is fitted and a bolt insertion hole into which a bolt inserted; a pair of fixing plates (31, 32) each having at least one large-diameter hole and a bolt insertion hole (31a, 32a) into which a bolt is inserted; and a bolt that is inserted into the bolt insertion hole (31 a) of the one fixing plate, the bolt insertion hole of the housing and the bolt insertion hole of the other fixing plate, and connects the housing with the pair of fixing plates (31, 32), wherein both axial end portions of the outer ring are held and fixed by the pair of fixing plates (31, 32) in the axial direction and the inner ring is positioned further inwardly of the large-diameter hole of the fixing plates (31, 32) in the radial direction, and the inner ring is rotatable with respect to the fixing plates 31, 32), the housing includes a housing main body having a cylindrical inner circumferential surface and a protruding portion extending from an axially middle part of the inner circumferential surface of the housing main body to the inside in the radial direction, the outer ring is arranged inwardly of the protruding portion in the radial direction, the bolt insertion hole is formed at the protruding portion, the fixing plates (31, 32) are fitted to stepped portions formed between the housing main body and the protruding portion, and the projections are engaged with the stepped portions, and the fixing plates (31, 32) are formed to have a thickness with which the fixing plate (31, 32) is accommodated at the stepped portion, characterized in that stepped portions are provided at both axial end portions of the outer circumferential surface of the outer ring. projections are provided on the inner circumferential surfaces of the large diameter holes of the pair of fixing plates (31, 32), the stepped portions of the outer ring at both axial end portions are engaged with the projections to restrict an axial movement of the bearing, and the axial length of the housing is equivalent to the axial length of the rolling bearing. at least one bearing having an inner ring and an outer ring that are mutually rotatable; a housing having at least one fitting hole into which the bearing is fitted and a bolt insertion hole into which a bolt inserted; a pair of fixing plates (31, 32) each having at least one large-diameter hole and a bolt insertion hole (31a, 32a) into which a bolt is inserted; and a bolt that is inserted into the bolt insertion hole (31 a) of the one fixing plate, the bolt insertion hole of the housing and the bolt insertion hole of the other fixing plate, and connects the housing with the pair of fixing plates (31, 32), wherein both axial end portions of the outer ring are held and fixed by the pair of fixing plates (31, 32) in the axial direction and the inner ring is positioned further inwardly of the large-diameter hole of the fixing plates (31, 32) in the radial direction, and the inner ring is rotatable with respect to the fixing plates 31, 32), the housing includes a housing main body having a cylindrical inner circumferential surface and a protruding portion extending from an axially middle part of the inner circumferential surface of the housing main body to the inside in the radial direction, the outer ring is arranged inwardly of the protruding portion in the radial direction, the bolt insertion hole is formed at the protruding portion, the fixing plates (31, 32) are fitted to stepped portions formed between the housing main body and the protruding portion, and the projections are engaged with the stepped portions, and the fixing plates (31, 32) are formed to have a thickness with which the fixing plate (31, 32) is accommodated at the stepped portion, characterized in that stepped portions are provided at both axial end portions of the outer circumferential surface of the outer ring. projections are provided on the inner circumferential surfaces of the large diameter holes of the pair of fixing plates (31, 32), the stepped portions of the outer ring at both axial end portions are engaged with the projections to restrict an axial movement of the bearing, and the axial length of the housing is equivalent to the axial length of the rolling bearing.