A bearing insertion apparatus comprising: a base; a movable carriage provided to be movable in a horizontal Z-axis direction on the base; and an apparatus main bod supported to be freely movable in a predetermined direction with respect to the movable carriage, wherein: the apparatus main body includes: an elongated hollow cylinder-shaped outer ring supporting cylinder having a distal end surface that is brought into contact with a side surface of an outer ring constituting a rolling bearing such that positioning of the rolling bearing in the Z-axis direction is performed; and an inner ring clamping mechanism gripping an inner peripheral surface of an inner ring constituting the rolling bearing by expanding and contracting a clamp main body provided at a portion protruding from a distal end of the outer ring supporting cylinder; and the apparatus main body is structured to be freely movable with respect to the movable carriage by being guided by a guide mechanism in a horizontal X-axis direction orthogonal to the Z-axis direction and in a vertical Y-axis direction orthogonal to both of the Z-axis direction and the X-axis direction, and the apparatus main body is floatingly supported in a state of being movable in the Y-axis direction within a predetermined range. a base; a movable carriage provided to be movable in a horizontal Z-axis direction on the base; and an apparatus main bod supported to be freely movable in a predetermined direction with respect to the movable carriage, wherein: the apparatus main body includes: an elongated hollow cylinder-shaped outer ring supporting cylinder having a distal end surface that is brought into contact with a side surface of an outer ring constituting a rolling bearing such that positioning of the rolling bearing in the Z-axis direction is performed; and an inner ring clamping mechanism gripping an inner peripheral surface of an inner ring constituting the rolling bearing by expanding and contracting a clamp main body provided at a portion protruding from a distal end of the outer ring supporting cylinder; and the apparatus main body is structured to be freely movable with respect to the movable carriage by being guided by a guide mechanism in a horizontal X-axis direction orthogonal to the Z-axis direction and in a vertical Y-axis direction orthogonal to both of the Z-axis direction and the X-axis direction, and the apparatus main body is floatingly supported in a state of being movable in the Y-axis direction within a predetermined range. the apparatus main body includes: an elongated hollow cylinder-shaped outer ring supporting cylinder having a distal end surface that is brought into contact with a side surface of an outer ring constituting a rolling bearing such that positioning of the rolling bearing in the Z-axis direction is performed; and an inner ring clamping mechanism gripping an inner peripheral surface of an inner ring constituting the rolling bearing by expanding and contracting a clamp main body provided at a portion protruding from a distal end of the outer ring supporting cylinder; and the apparatus main body is structured to be freely movable with respect to the movable carriage by being guided by a guide mechanism in a horizontal X-axis direction orthogonal to the Z-axis direction and in a vertical Y-axis direction orthogonal to both of the Z-axis direction and the X-axis direction, and the apparatus main body is floatingly supported in a state of being movable in the Y-axis direction within a predetermined range.