A pump with a motor, characterized by comprising: a pump housing; a motor housing configured to store a stator and a rotor and rotatably support one end of a rotating shaft of the rotor; and a connecting structure configured to connect the motor housing to the pump housing, wherein the connecting structure includes: a motor connecting portion provided at an end of the pump housing; and a pump connecting portion provided at an end of the motor housing, the motor connecting portion includes: a bearing configured to rotatably support the other end of the rotating shaft; a plurality of through holes extending in an axial direction of the rotating shaft; and the pump connecting portion includes: a plurality of connecting pieces inserted into the plurality of through holes, respectively, and caulked on the motor connecting portion; characterized in that, the pump housing is made of a plastic material; the motor housing including a portion made of a metal material; the motor connecting portion further includes a projection projecting to a side of the motor housing in parallel to an axis of the rotating shaft; and the pump connecting portion further includes: a first hole in which the bearing is fitted; and a second hole in which the projection is fitted. a pump housing; a motor housing configured to store a stator and a rotor and rotatably support one end of a rotating shaft of the rotor; and a connecting structure configured to connect the motor housing to the pump housing, wherein the connecting structure includes: a motor connecting portion provided at an end of the pump housing; and a pump connecting portion provided at an end of the motor housing, the motor connecting portion includes: a bearing configured to rotatably support the other end of the rotating shaft; a plurality of through holes extending in an axial direction of the rotating shaft; and the pump connecting portion includes: a plurality of connecting pieces inserted into the plurality of through holes, respectively, and caulked on the motor connecting portion; characterized in that, the pump housing is made of a plastic material; the motor housing including a portion made of a metal material; the motor connecting portion further includes a projection projecting to a side of the motor housing in parallel to an axis of the rotating shaft; and the pump connecting portion further includes: a first hole in which the bearing is fitted; and a second hole in which the projection is fitted. a motor connecting portion provided at an end of the pump housing; and a pump connecting portion provided at an end of the motor housing, the motor connecting portion includes: a bearing configured to rotatably support the other end of the rotating shaft; a plurality of through holes extending in an axial direction of the rotating shaft; and the pump connecting portion includes: a plurality of connecting pieces inserted into the plurality of through holes, respectively, and caulked on the motor connecting portion; characterized in that, the pump housing is made of a plastic material; the motor housing including a portion made of a metal material; the motor connecting portion further includes a projection projecting to a side of the motor housing in parallel to an axis of the rotating shaft; and the pump connecting portion further includes: a first hole in which the bearing is fitted; and a second hole in which the projection is fitted. a bearing configured to rotatably support the other end of the rotating shaft; a plurality of through holes extending in an axial direction of the rotating shaft; and the pump connecting portion includes: a plurality of connecting pieces inserted into the plurality of through holes, respectively, and caulked on the motor connecting portion; characterized in that, the pump housing is made of a plastic material; the motor housing including a portion made of a metal material; the motor connecting portion further includes a projection projecting to a side of the motor housing in parallel to an axis of the rotating shaft; and the pump connecting portion further includes: a first hole in which the bearing is fitted; and a second hole in which the projection is fitted. a plurality of connecting pieces inserted into the plurality of through holes, respectively, and caulked on the motor connecting portion; characterized in that, the pump housing is made of a plastic material; the motor housing including a portion made of a metal material; the motor connecting portion further includes a projection projecting to a side of the motor housing in parallel to an axis of the rotating shaft; and the pump connecting portion further includes: a first hole in which the bearing is fitted; and a second hole in which the projection is fitted. a first hole in which the bearing is fitted; and a second hole in which the projection is fitted.