Abstract: A writing instrument wherein a rear cap is rotatably connected through a connector to a rear end of an outer tube into which a core pipe is axially slidably inserted, a guide member for an eraser is axially slidably inserted into the rear cap for axial engagement, a spiral member is spirally connected to an eraser receiving member which supports an eraser axially slidably inserted into a spiral member for axial engagement, the spiral member having a front end axially slidably connected to the connector for axial engagement, and the eraser guide member is urged in a withdrawing direction by means of an elastic body so that the guide member is held at a fixed projected position during non-knocking.