A motion determining apparatus includes a processor comprising hardware. The processor is configured to: acquire first and second compressed data formed by compressing each of first and second images sequentially captured inside a subject by a body-insertable apparatus provided with an image sensor and an illumination device that performs irradiation with illumination light, and a parameter with regard to the illumination device at a time of capturing the first and second images with the image sensor calculate a difference between a data amount of the first compressed data and a data amount of the second compressed data compare the difference with a first threshold value compare the parameter with at least one reference value and determine whether a motion of the body-insertable apparatus is larger than a predetermined value based on comparison results of comparing the difference and comparing the parameter with at least one reference value.
