A workpiece installation method for a machining apparatus, the method comprising: placing a reference workpiece on a table; adjusting a posture of the reference workpiece on the table to make the posture of the reference workpiece a workpiece reference posture; setting a configuration of a camera configured to capture an image of the table to a target configuration in which a viewpoint position of the camera is a reference viewpoint position and a line-of-sight direction of the camera is a reference line-of-sight direction; obtaining a reference image that shows the reference workpiece whose posture has been adjusted and that has been captured by the camera whose configuration has been set to the target configuration; setting workpiece reference lines (RL1 to RL4) on a boundary of a first image area occupied by the reference workpiece in the reference image, by a user; storing workpiece reference line positions in a memory, the workpiece reference lines passing through the workpiece reference line positions in the reference image; placing a workpiece substantially identical in shape and size to the reference workpiece on one table out of the table from which the reference workpiece has been removed and an additional table that is different from the table and that has been provided in place of the table; obtaining a measurement image that shows the workpiece and that has been captured by the camera whose configuration has been set to the target configuration; generating, using a processor, a measurement combined image in which the workpiece reference lines are superimposed on the measurement image and which shows the workpiece reference lines pass through positions respectively identical to the workpiece reference line positions; and adjusting a posture of the workpiece on the one table such that a boundary of a second image area occupied by the workpiece in the measurement combined image is shown to be substantially parallel to or substantially coincident with the workpiece reference lines. placing a reference workpiece on a table; adjusting a posture of the reference workpiece on the table to make the posture of the reference workpiece a workpiece reference posture; setting a configuration of a camera configured to capture an image of the table to a target configuration in which a viewpoint position of the camera is a reference viewpoint position and a line-of-sight direction of the camera is a reference line-of-sight direction; obtaining a reference image that shows the reference workpiece whose posture has been adjusted and that has been captured by the camera whose configuration has been set to the target configuration; setting workpiece reference lines (RL1 to RL4) on a boundary of a first image area occupied by the reference workpiece in the reference image, by a user; storing workpiece reference line positions in a memory, the workpiece reference lines passing through the workpiece reference line positions in the reference image; placing a workpiece substantially identical in shape and size to the reference workpiece on one table out of the table from which the reference workpiece has been removed and an additional table that is different from the table and that has been provided in place of the table; obtaining a measurement image that shows the workpiece and that has been captured by the camera whose configuration has been set to the target configuration; generating, using a processor, a measurement combined image in which the workpiece reference lines are superimposed on the measurement image and which shows the workpiece reference lines pass through positions respectively identical to the workpiece reference line positions; and adjusting a posture of the workpiece on the one table such that a boundary of a second image area occupied by the workpiece in the measurement combined image is shown to be substantially parallel to or substantially coincident with the workpiece reference lines.