An elevator hoisting machine comprising: a motor comprising: a motor main body; and a motor shaft that is rotated by the motor main body; a coupling shaft comprising: a boss portion; and a rotation detector mounting shaft portion that protrudes outward from the boss portion away from the motor shaft, the coupling shaft being mountable to and removable from an end portion of the motor shaft; a mounting member on which is disposed a penetrating aperture through which the rotation detector mounting shaft portion is passed; and a rotation detector that is mounted to the rotation detector mounting shaft portion, the elevator hoisting machine being characterized in that: an inner circumferential surface of the penetrating aperture is an inclined pressing surface that is inclined relative to a shaft axis of the motor shaft such that an inside diameter of the penetrating aperture increases continuously toward the motor shaft; an inclined bearing surface that is inclined relative to a shaft axis of the coupling shaft is disposed on the boss portion so as to be formed into an annular shape around the shaft axis of the coupling shaft, and such that an outside diameter of the boss portion increases continuously toward the motor shaft; and the inclined pressing surface is able to contact the inclined bearing surface by the mounting member being displaced toward the motor shaft. a motor comprising: a motor main body; and a motor shaft that is rotated by the motor main body; a motor main body; and a motor shaft that is rotated by the motor main body; a coupling shaft comprising: a boss portion; and a rotation detector mounting shaft portion that protrudes outward from the boss portion away from the motor shaft, the coupling shaft being mountable to and removable from an end portion of the motor shaft; a boss portion; and a rotation detector mounting shaft portion that protrudes outward from the boss portion away from the motor shaft, a mounting member on which is disposed a penetrating aperture through which the rotation detector mounting shaft portion is passed; and a rotation detector that is mounted to the rotation detector mounting shaft portion, the elevator hoisting machine being characterized in that: an inner circumferential surface of the penetrating aperture is an inclined pressing surface that is inclined relative to a shaft axis of the motor shaft such that an inside diameter of the penetrating aperture increases continuously toward the motor shaft; an inclined bearing surface that is inclined relative to a shaft axis of the coupling shaft is disposed on the boss portion so as to be formed into an annular shape around the shaft axis of the coupling shaft, and such that an outside diameter of the boss portion increases continuously toward the motor shaft; and the inclined pressing surface is able to contact the inclined bearing surface by the mounting member being displaced toward the motor shaft. an inner circumferential surface of the penetrating aperture is an inclined pressing surface that is inclined relative to a shaft axis of the motor shaft such that an inside diameter of the penetrating aperture increases continuously toward the motor shaft; an inclined bearing surface that is inclined relative to a shaft axis of the coupling shaft is disposed on the boss portion so as to be formed into an annular shape around the shaft axis of the coupling shaft, and such that an outside diameter of the boss portion increases continuously toward the motor shaft; and the inclined pressing surface is able to contact the inclined bearing surface by the mounting member being displaced toward the motor shaft.