1. A motor function evaluation system for evaluating the motor function of a wrist motion of a subject, which comprises: a display configured for displaying image information including a target image and a cursor image for tracking the target image; a device configured for use by the subject for moving the cursor image by using wrist motion; a detector configured for detecting the state of tracking of the target image by the cursor image; a sensor configured for detecting myoelectric signals of extensor carpi radialis brevis muscle and extensor carpi radialis longus muscle (ECR), extensor carpi ulnaris muscle (ECU), flexor carpi ulnaris muscle (FCU) and flexor carpi radialis muscle (FCR) as the muscle active state of muscles related to the wrist motion of the subject using the device; an analyzer configured for analyzing the tracking state detected by the detector and the muscle active state detected by the sensor; and an evaluator configured for evaluating the motor function of the wrist motion of the subject by using results of analysis obtained by the analyzer as indexes.