PURPOSE: A writing instrument with a touch pen function is provided to reduce costs and increase efficiency of using a pen. CONSTITUTION: An external housing(110) has a fixed receiving space. An inner housing receives a core. A handwriting unit is formed on an end in front of the inner housing. A rear end cap unit(140) controls input/output of the core and prevents separation of the core. A frontal end cap unit(150) protects the handwriting unit of the inner housing.
