The present invention provides writing instruments having a mechanism for extending and retracting a writing tip and advancing a lead by rotational operation. The writing instrument is comprised of a front tubular member (1); a front inner tubular member (2) disposed within the front tubular member (1); a refill (3) inserted into the front inner tubular member (2); and a driver (10) mounted in the front tubular member (1) and the front inner tubular member (2). The driver (10) is allowed to rotate but not be axial displaced relative to the front tubular member (1) and the front inner tubular member (2). A rear tubular member (5) is detachably connected to the driver (10) so as not to allow rotation relative to the driver (10). A rear inner tubular member (4) is inserted in the driver (10). The rear inner tubular member (4) and the driver (10) interengage with each other by engagement between at least one axial groove (11) and corresponding projections (12). The writing instrument further comprises an inclined path (7) provided on one of either front inner tubular member (2) or the rear inner tubular member (4). The inclined path (7) extends obliquely relative to the axial line of the writing instrument from a beginning end (7A) and a terminal end (7B). A projection (8) provided on the other of either the front inner tubular member (2) or the rear inner tubular member (4), engages the inclined path (7).