There are a few of reports of delayed rupture of flexor tendon around the wrist and hand by attrition. Only 4 cases of delayed flexor tendon rupture of finger except rupture of flexor pollicis longus after Cellos fracture were reported until now. Several causes of the delayed rupture of the tendon around the wrist and hand were reported by many authors. Cellos fracture is one of the cause of the attritional rupture. But the frequency of the attritonal rupture of the flexor tendon was only one-third of the extensor tendons. Furthermore, flexor tendons of the finger were less commonly affected than that of the thumb by their anatomical features. We would like to report a very rare case of delayed rupture of flexor digitorum profundus on 73 year old male patient by attrition on the bony spur which was formed by malunion of distal radial fracture about 10 years ago. They were treated by direct repair for ring finger and free tendon graft with flexor digitorum sublimis of middle finger for little finger. After 1 year follow up, range of motion and flexion power were recovered to nearly normal.