A special path generating device includes a base, a first axis slide assembly, a second axis slide assembly, a working portion, a driving portion, a first cam and a second cam. This first axis slide assembly includes a first bar and a first slide. The second axis slide assembly includes a second bar and a second slide. This working portion is mounted on the second slide that has two contacting portions. The driving portion is mounted on the base. When the driving portion drives the driving shaft rotating, the first cam and the second cam rotate accordingly and makes the working portion generating a special path. It can generate a constant-speed circular movement. It is easy to control. In addition, its volume is small.