An animal exercise assist device and animal activity information monitoring system and method are provided. The animal exercise assist device is mounted on an animal so as to assist exercise of the animal and includes: a sensing unit that measures movement of the animal a control unit that generates activity information of the animal on the basis of a current degree of activity acquired by analyzing the movement a memory that stores a target degree of activity of the animal and the activity information generated by the control unit and a display unit that displays the activity information in a predetermined format. The display unit displays a ratio of the current degree of activity to the target degree of activity.
