Different types of devices, from the simplest (medical walkers) to the most technologically advanced ones (mechatronic devices), are widely used to support the rehabilitation process for people who suffered strokes or have other disabilities—especially to enhance their mobility. This article presents a new mechatronic system for gait reeducation, which consists of two main components: training treadmill and body weight support system. The device is also equipped with sensors for measuring the rope inclination angle, rope tension and foot pressure on the ground. The transmission of measurement and control signals between the computer with control system and the electromechanical part of the device is realized by means of three real-time boards. This publication covers certain issues related to the device design process, integration of the main components, as well as the description of the developed treadmill speed adaptation algorithm and experimental verification of such control system. The speed of treadmill belt is adjusted by a feedback loop with a rope inclination angle measurement. Because of the kind of the connection of the treadmill (the control signals are sent to the buttons in the treadmill control panel) and related limitations, a proper conversion of the control signal was required, from a continuous one to a digital square wave signal with variable period. Developing an optimal treadmill speed control algorithm in this case was an interesting engineering challenge.