The present invention provides a sharpening completion detection mechanism that does not apply a heavy load to a core tip, and especially proposes a mechanism that moves a pencil in an ejection direction immediately when the sharpening completion detection mechanism detects completion of sharpening to mitigate damage to the core. Specifically, a pencil sharpener according to the present invention includes: a slide unit that translates in pencil insertion and pencil ejection directions; a pencil biasing means supported by the slide unit; a slide locking means that locks a translation position of the slide unit upon the slide unit translating in the insertion direction; and a slide unit unlocking means that releases the lock for the translation position of the slide unit upon the sharpening completion detection means detecting a fully sharpened state of the pencil, and includes slide unit ejecting means that biases the slide unit in the ejection direction with energy stored by movement of the slide unit to a lock position.