member 2 in which bore 24 the rear end of a lead tube 25 for guiding the lead 7 and holding it to resist bending forces exerted thereon during writing is inserted and fixedly held a hole 26 of a small diameter is formed in the longitudinal direction in the nose member 2 at a position above and spaced apart from the bore 24 through this hole 26 the rear end of a sensor 27 having elasticity such as a piece of piano wire is inserted and slidably held the front end portion of the sensor 27 is slightly arched so as to approach the front end of the lead 7 while the rear end of the sensor 27 is bent so as to abut against the front end face of the holder 20 the operation of the mechanical pencil of the above described construction according to this invention is as follows when a new length of lead 7 is fed to the front portion of the pencil m through the clamping mechanism 4 the actuating button not shown provided at the rear end of the magazine 5 is pushed into the housing 1 or forward in order to open.