A writing tool includes a writing unit, a capillary member, a dispensing unit, and a replaceable ink cartridge. The capillary member, the dispensing unit, and the replaceable ink cartridge are mounted in the writing unit. The dispensing unit contacts the capillary member and has at least one cutting portion. The replaceable ink cartridge accommodates ink therein and has a film at one end thereof. The replaceable ink cartridge can be installed in the dispensing unit and the film can be pierced and cut by the at least one cutting portion. The ink flows through the film and is delivered to the writing unit via the capillary member and the dispensing unit for writing. The writing tool can thus dispense the ink fluently and leave no residual ink.