This paper presents an upper-limb rehabilitation device that provides symmetric bilateral movements with motion measurements using inertial sensors. Mirror therapy is one of widely used methods for rehabilitation of impaired side movements because voluntary movement of the unimpaired side facilitates reorganizational changes in the motor cortex. The developed upper-limb exoskeleton was equipped with two brushless DC motors that helped generate three axes of upper-limb movements corresponding to other arm movements that were measured using inertial sensors. In this study, inertial sensors were used to estimate the joint angles for three target upper-limb movements: elbow flexion and extension (flex/ext), wrist flex/ext, and forearm pronation and supination (pro/sup). Elbow flex/ext was performed by the actuator that was directly attached to the elbow joint. The actuation of the forearm pro/sup and wrist flex/ext shared one motor using a developed cable-driven mechanism, and two types of motion were selectively performed. We assessed the feasibility of the proposed mirror-image device with the accuracy and precision of the motion estimation and the actuation of joint movements. An individual could perform most upper-limb movements for activities of daily living using the proposed device.