Abstract: A writing tool such as a ball pen or the like including an openable decorative article at a shaft end comprises a shaft member serving as a casing for the writing tool, a core vertically displaceably received in the shaft member, an actuation member connected to the core, a movable member adapted to move when the core is downwardly displaced at the time of practical use of the writing tool, and a support member for supporting the decorative article. The actuation member includes a fixing piece and an actuation piece protruded outside of the shaft member. When an user displaces the actuation piece in the downward direction with his finger for practical use of the writing tool, an assembly of the movable member and the support member is displaced in the same direction, whereby the decorative article is expanded via a flange integrated with the support member as if petals of a flower are opened. At this time, a butterfly-shaped accessory fixedly mounted on the central part of the support member appears.