An electric pump and an electric pump mounting structure comprising: a housing (62, 60); an annular stator portion that has a coil portion; an outer rotor portion that is arranged coaxially with the stator portion, at a position on an inner side of the stator portion, and that is rotated based on a magnetic field generated by the coil portion; and an inner rotor that is rotatably supported, at a position on an inner side of the outer rotor portion, by a support shaft portion that is supported at an axial position offset from a rotation axis of the outer rotor portion, and that has an outer peripheral surface that is engaged with an inner peripheral surface of the outer rotor portion, wherein the housing (62, 60) is formed of a first housing and a second housing that are separated from each other in an axial direction, the first housing is fixed to the support shaft portion, the second housing is fitted onto the support shaft portion from one side of the support shaft portion in the axial direction, and is fixed to a portion of the support shaft portion, the portion being on the one axial side, and the stator portion is clamped between the first housing and the second housing fixed to the support shaft portion from both sides in the axial direction, and the outer rotor portion and the inner rotor are rotatably held between the first housing and the second housing from both sides in the axial direction, characterized in that the support shaft portion has a hollow shape, and has a through-hole extending in the axial direction, and the support shaft portion is structured so as to be fixed to a mounting-target member (α) by inserting a fixing member (α1) into the through-hole of the support shaft portion. a housing (62, 60); an annular stator portion that has a coil portion; an outer rotor portion that is arranged coaxially with the stator portion, at a position on an inner side of the stator portion, and that is rotated based on a magnetic field generated by the coil portion; and an inner rotor that is rotatably supported, at a position on an inner side of the outer rotor portion, by a support shaft portion that is supported at an axial position offset from a rotation axis of the outer rotor portion, and that has an outer peripheral surface that is engaged with an inner peripheral surface of the outer rotor portion, wherein the housing (62, 60) is formed of a first housing and a second housing that are separated from each other in an axial direction, the first housing is fixed to the support shaft portion, the second housing is fitted onto the support shaft portion from one side of the support shaft portion in the axial direction, and is fixed to a portion of the support shaft portion, the portion being on the one axial side, and the stator portion is clamped between the first housing and the second housing fixed to the support shaft portion from both sides in the axial direction, and the outer rotor portion and the inner rotor are rotatably held between the first housing and the second housing from both sides in the axial direction, characterized in that the support shaft portion has a hollow shape, and has a through-hole extending in the axial direction, and the support shaft portion is structured so as to be fixed to a mounting-target member (α) by inserting a fixing member (α1) into the through-hole of the support shaft portion.