A turbocharger comprising: a shaft; a bearing housing accommodating a bearing rotatably supporting the shaft; a turbine housing accommodating a turbine wheel arranged at one end of the shaft in an axial direction; a uniting member uniting the bearing housing and the turbine housing; and a back plate arranged between the turbine wheel and the bearing housing, wherein the bearing housing includes a first connection section protruded in a radial direction of the shaft, the first connection section having a first face extended in the radial direction, the turbine housing includes a second connection section protruded in the radial direction of the shaft, the second connection section having a second face extended in the radial direction and being faced to the first face, the uniting member holds the first connection section and the second connection section by being fitted to the first connection section and the second connection section from the outside, at least one of the first face and the second face includes a ring-shaped concave portion on an inner side in the radial direction of the shaft with a sealing member arranged at the ring-shaped concave portion, the sealing member is formed into a ring shape and configured to be elastically deformable in the axial direction of the shaft, the bearing housing further includes an end face formed on a side toward the turbine wheel with respect to the first connection section in the axial direction of the shaft and extended in the radial direction of the shaft, an outer side face defined by a step formed between the first face of the first connection section and the end face, and a protruded section protruded from the end face in the axial direction of the shaft, the turbine housing further includes a back plate supporting section arranged on a side toward the turbine wheel with respect to the second connection section in the axial direction of the shaft and extended radially inward in the radial direction of the shaft and a fitting section extended in the axial direction of the shaft, integrally connected at a lower end thereof to the second connection section and connected at an upper end thereof to the back plate supporting section, and fitted to the bearing housing with an inner side face thereof opposed to the outer side face of the bearing housing, and the back plate is formed into a ring shape having an outer circumferential edge section and an inner circumferential edge section and is arranged so that the outer circumferential edge section extended in the radial direction of the shaft is interposed between the back plate supporting section and the end face, characterised in that the inner circumferential edge section is fitted to an outer circumference of the protruded section. a shaft; a bearing housing accommodating a bearing rotatably supporting the shaft; a turbine housing accommodating a turbine wheel arranged at one end of the shaft in an axial direction; a uniting member uniting the bearing housing and the turbine housing; and a back plate arranged between the turbine wheel and the bearing housing, wherein the bearing housing includes a first connection section protruded in a radial direction of the shaft, the first connection section having a first face extended in the radial direction, the turbine housing includes a second connection section protruded in the radial direction of the shaft, the second connection section having a second face extended in the radial direction and being faced to the first face, the uniting member holds the first connection section and the second connection section by being fitted to the first connection section and the second connection section from the outside, at least one of the first face and the second face includes a ring-shaped concave portion on an inner side in the radial direction of the shaft with a sealing member arranged at the ring-shaped concave portion, the sealing member is formed into a ring shape and configured to be elastically deformable in the axial direction of the shaft, the bearing housing further includes an end face formed on a side toward the turbine wheel with respect to the first connection section in the axial direction of the shaft and extended in the radial direction of the shaft, an outer side face defined by a step formed between the first face of the first connection section and the end face, and a protruded section protruded from the end face in the axial direction of the shaft, the turbine housing further includes a back plate supporting section arranged on a side toward the turbine wheel with respect to the second connection section in the axial direction of the shaft and extended radially inward in the radial direction of the shaft and a fitting section extended in the axial direction of the shaft, integrally connected at a lower end thereof to the second connection section and connected at an upper end thereof to the back plate supporting section, and fitted to the bearing housing with an inner side face thereof opposed to the outer side face of the bearing housing, and the back plate is formed into a ring shape having an outer circumferential edge section and an inner circumferential edge section and is arranged so that the outer circumferential edge section extended in the radial direction of the shaft is interposed between the back plate supporting section and the end face,