To eliminate the problem that a return spring is disengaged or deformed in an assembling operation and to improve assembling properties, by a method wherein the return spring is incorporated beforehand in a cam tube together with a rotor and a knock rod, and fitted to a holder tube.

In a knock type writing implement, a knock mechanism part is provided in the rear of the holder tube, and a writing tip part of a ballpoint pen refill is projected and withdrawn from the fore end opening in the end of the holder tube by moving forward and backward a knock part projecting from the rear end of the holder tube. The knock rod and the rotor having cams engaging with a cam groove of the cam tube are inserted into the cam tube so that they can be shifted axially, and a support seat is so engaged with a substantial front end of the cam tube as to be prevented from slipping off. On the occasion, the return spring is laid between a step in the front end of the cam of the rotor and the support seat, while the rotor is always urged toward the rear of the holder tube by the return spring and the cam tube is fixed to the holder tube.