In order to investigate the usefulness of an electromagnetic three-dimensional measuring device as a monitor for the side shift exercise, the evaluation by the well-trained physical therapist as to whether the exercise was properly performed or not was compared with the evaluation using data obtained by the device. The side shift exercises performed by twenty-four female patients with idiopathic scoliosis were classified as "good," "rotation," or "bend" by the well-trained physical therapist. By the use of the data obtained by the electromagnetic three-dimensional measuring device, whether the exercise was "rotation" or not could be predicted with 100% sensitivity and 100% specificity, and whether the exercise was "bend" or not could be predicted with 83% sensitivity and 100% specificity. These results suggested that the electromagnetic three-dimensional measuring device could be a useful monitor for the side shift exercise.