Abstract: A ball-point pen for water-soluble ink having a barrel with a vent hole, a cylindrical ink reservoir covered except at its exposed front and rear ends, and an ink feed core for supplying ink from the reservoir to a ball at the pen writing tip is provided with a hollow inner cover member comprising a cylindrical holding part for covering and holding a relatively long front portion of the reservoir and a cylindrical shielding part for partitioning the front exposed part of the reservoir and the feed core from the vent hole, the inner cover member being secured within the barrel by press-fitting the front end of the shielding part into a bore of the front end part of the barrel. Passages are provided for communication between the vent hole and the rear exposed end of the reservoir. Leakage of ink due to causes such as temperature change and impact force imparted to the barrel in the longitudinal direction thereof is thereby prevented.