A bearing structure comprising: a housing comprising a first housing portion having a cross-sectionally generally-semicircular concave portion and a second housing portion having a cross-sectionally generally-semicircular concave portion forming together with the concave portion of the first housing portion a cross-sectionally generally-circular support hole; and a two-division rolling bearing comprising a pair of two-division outer rings (203a, 203b) mounted within the support hole of the housing in closely-contacted relation thereto, a plurality of rolling elements so mounted as to be able to roll on inner side surfaces of the two two-division outer rings (203a, 203b), and a pair of two-division cages (205a, 205b) holding the rolling elements such that the rolling elements are arranged at generally equal intervals in a circumferential direction, a shaft being internally fitted to the two-division rolling bearing; characterized in that: said first housing portion and said second housing portion are mounted in offset relation to each other in a radial direction so that at mating surfaces of circumferential end portions of said pair of two-division outer rings (203a, 203b), the outer ring end portions disposed at an upstream side with respect to a direction of rotation of the shaft can form radially inwardly-projecting steps, respectively; and a size of said step is so set as to be generally equal to the amount of elastic deformation by a rolling element load which the outer ring end portion disposed at the upstream side with respect to the direction of rotation of the shaft receives from the rolling elements. a housing comprising a first housing portion having a cross-sectionally generally-semicircular concave portion and a second housing portion having a cross-sectionally generally-semicircular concave portion forming together with the concave portion of the first housing portion a cross-sectionally generally-circular support hole; and a two-division rolling bearing comprising a pair of two-division outer rings (203a, 203b) mounted within the support hole of the housing in closely-contacted relation thereto, a plurality of rolling elements so mounted as to be able to roll on inner side surfaces of the two two-division outer rings (203a, 203b), and a pair of two-division cages (205a, 205b) holding the rolling elements such that the rolling elements are arranged at generally equal intervals in a circumferential direction, a shaft being internally fitted to the two-division rolling bearing; characterized in that: said first housing portion and said second housing portion are mounted in offset relation to each other in a radial direction so that at mating surfaces of circumferential end portions of said pair of two-division outer rings (203a, 203b), the outer ring end portions disposed at an upstream side with respect to a direction of rotation of the shaft can form radially inwardly-projecting steps, respectively; and a size of said step is so set as to be generally equal to the amount of elastic deformation by a rolling element load which the outer ring end portion disposed at the upstream side with respect to the direction of rotation of the shaft receives from the rolling elements. said first housing portion and said second housing portion are mounted in offset relation to each other in a radial direction so that at mating surfaces of circumferential end portions of said pair of two-division outer rings (203a, 203b), the outer ring end portions disposed at an upstream side with respect to a direction of rotation of the shaft can form radially inwardly-projecting steps, respectively; and a size of said step is so set as to be generally equal to the amount of elastic deformation by a rolling element load which the outer ring end portion disposed at the upstream side with respect to the direction of rotation of the shaft receives from the rolling elements.