A fixed scroll positioning apparatus, suitable for use in an assembly process of a scroll fluid machinery, for positioning a fixed scroll on the basis of a positional relationship between a volute wrap of the fixed scroll and a volute wrap of a movable scroll of a scroll machinery that includes a drive motor, comprising: a fixing member for fixing an assembly body composed of an integrated combination of the movable scroll, a crank shaft engaged with the movable scroll, a housing member serving as a bearing for the crank shaft, and the drive motor for driving the crank shaft; power supply means for supplying electric power to the drive motor to shift the movable scroll of the assembly body; determining means for determining a stirring distance and a stirring direction of the fixed scroll by shifting the movable scroll engaged with the fixed scroll; and a stirring mechanism for stirring the fixed scroll according to the stirring distance and the stirring direction determined by the determining means, characterised in that the power supply means includes an inverter for supplying power to the drive motor, and a driver for controlling operation of the inverter, the driver determines an instruction value relating to an output current value and an output frequency of the inverter such that the drive motor rotates at a predetermined rotation speed, the driver outputs an instruction relating to switching timing and the like to the inverter such that the output current value and the output frequency of the inverter correspond to the instruction value, the determining means detects change in rotational torque of the drive motor during the rotation of the crank shaft with the use of the instruction value relating to the output current value of the inverter determined by the driver, and the determining means determines the stirring distance and the stirring direction of the fixed scroll on the basis of the change in rotation torque of the drive motor. a fixing member for fixing an assembly body composed of an integrated combination of the movable scroll, a crank shaft engaged with the movable scroll, a housing member serving as a bearing for the crank shaft, and the drive motor for driving the crank shaft; power supply means for supplying electric power to the drive motor to shift the movable scroll of the assembly body; determining means for determining a stirring distance and a stirring direction of the fixed scroll by shifting the movable scroll engaged with the fixed scroll; and a stirring mechanism for stirring the fixed scroll according to the stirring distance and the stirring direction determined by the determining means, characterised in that the power supply means includes an inverter for supplying power to the drive motor, and a driver for controlling operation of the inverter, the driver determines an instruction value relating to an output current value and an output frequency of the inverter such that the drive motor rotates at a predetermined rotation speed, the driver outputs an instruction relating to switching timing and the like to the inverter such that the output current value and the output frequency of the inverter correspond to the instruction value, the determining means detects change in rotational torque of the drive motor during the rotation of the crank shaft with the use of the instruction value relating to the output current value of the inverter determined by the driver, and the determining means determines the stirring distance and the stirring direction of the fixed scroll on the basis of the change in rotation torque of the drive motor.