Disclosed is a double chuck type mechanical pencil and an internal writing mechanism thereof comprising a feed chuck for feeding a normal lead, and a tip chuck for holding the tip of a lead for reducing a residual lead. The double chuck type mechanical pencil comprises a lead tank provided movably in a longitudinal direction within a barrel, a feed chuck connected to the lead tank to feed leads, a chuck ring loosely fitted in the feed chuck, a sleeve provided externally of the feed chuck, a chuck spring provided between the sleeve and the lead tank, an inner tube provided externally of the sleeve and movable integrally with the sleeve, a cushion spring provided between the inner tube and the barrel, a tip chuck provided on the end part of the inner tube, a tip ring provided externally of the tip chuck, and a tip spring provided between the tip chuck and the inner tube.