A retractable pen includes a barrel, an ink cartridge, a limiting member, a shifting member and a deformable member. When the shifting member is moved relative to the limiting member between a first position and a third position, the ink cartridge can be moved from a retracted position to an extended position or from the extended position to the retracted position. When the ink cartridge is located at the extended position, the deformable member can be further compressed by between the shifting member and the ink cartridge, allowing the shifting member to be moved further from the third position to a second position closer to the ink cartridge. When the shifting member is located at the second position, the ink cartridge is continuously held to the extended position and pressed against a lead-out opening of the barrel without the risk of swaying when a user writes with the retractable pen.