A parts assembly includes a housing including a first part assembly hole on which a first apparatus component is assembled, the first apparatus component being fixed to the housing by a caulking for forming a caulking portion by a deformation of a bearing surface of the housing on which the first apparatus component is seated. The housing includes a second part assembly hole provided in the vicinity of the caulking portion and on which a second apparatus component is assembled. The housing includes a sacrificial deformation portion deformed by a force applied to the housing when the bearing surface is deformed by the caulking, the sacrificial deformation portion attenuating a force propagated to a portion including the second part assembly hole where the second apparatus component is assembled.