Retractable pen

A retractable pen adapted for being accommodated in a portable electronic device, the retractable pen comprising:

• a housing;
• a shaft fixed in the housing and having a first ratcheting structure;
• a cap having a second ratcheting structure movably engaged with the first ratcheting structure;
• a driving member rotatably sheathing the shaft and located in the cap, the driving member having a third ratcheting structure;
• and
• an elastic member sheathing the shaft and leaning against the shaft and the driving member, wherein the elastic member constantly drives the driving member toward the first ratcheting structure or the second ratcheting structure;
• in a first state, the driving member is driven by the elastic member so that the third ratcheting structure leans against and is blocked by the first ratcheting structure;
• and in a second state, the driving member is driven by the elastic member so that the third ratcheting structure is movably engaged with the second ratcheting structure and leans against and is blocked by the first ratcheting structure so as to push the cap away from the housing.