In order to offer a method for the rehabilitation of injured fingers and a means of quantitative detection and evaluation, an exoskeleton based continuous passive motion (CPM) machine is presented in this paper. Corresponding to each finger of human hand, the CPM machine has 4 degrees of freedom (DOF) driven by two DC motors. The joint force and position sensors are all integrated into the machine. The device can be easily attached and also be adjusted to fit different hand sizes. During the injured fingerpsilas flexion and extension motion the machine can always exert perpendicular forces on the finger phalanges, meanwhile it can achieve the precise control of scope, force and speed of the moving fingers. In order to control the CPM machine, we have also designed an embedded control system based on S3C2410 (a kind of 32-bit RISC microprocessor). The whole system is open-ended for new functions and applications. The function modularization method provides a new thinking of design for the control system.