In a mechanical pencil, a tubular lead reservoir is connected to the rearward end of a lead chuck. A cylindrical weight is fitted slidably around the lead reservoir and is adapted to strike against the chuck to open the same to allow forward feed of the lead when a forward shake is applied to the pen barrel. In order to prevent forward feed of the lead as a result of unintended forward shake while carrying the pencil, a slider disposed rearwardly of the lead reservoir has a radially outwardly extending engagement projection which is adapted to slidably engage either a longitudinal guide slot in the pen barrel or a lateral slot circumferentially and rearwardly extending in the pen barrel. When the engagement projection is in engagement with the lateral slot, the chuck is caused to take an advanced position in which the chuck is open so that a forward stroke cannot feed the lead forward.