A pen holding device configured to hold an electronic pen which has a first core that is elongated and is replaceable. The pen holding device includes a casing having an electronic pen holder that is configured to hold the electronic pen in an erect state or a laid state, and at least one refill core holder which is provided inside the casing and is configured to grasp a second core, which is a refill core for the electronic pen, in a direction different from a longitudinal direction of the electronic pen when the electronic pen is held in the erect state.