A retractable writing instrument includes a push member including a clip and a protruding and retracting mechanism that causes a pen point to protrude from and retract into a front end of the barrel at a frontward press on the push member, without the push member rotating with respect to the instrument. The protruding and retracting mechanism includes cam teeth and cam grooves formed in an inner face of the barrel, a rotary member including protuberances engageable alternately with the cam teeth or the cam grooves, a cam member connected to the push member and includes cam projections rotating the rotary member, and engagement projections engaged with the cam grooves in the inner face of the barrel so as to be movable in the longitudinal direction; and a resilient element that biases the writing element rearward. The push member and the cam member are in detent engagement with each other.