To provide a capless writing utensil which has a pen point desiccation checking mechanism and prevents a foreign substance such as dust from intruding through an apex opening.

The operation of this capless writing utensil is as follows: a support is arranged at the apex side part of a barrel 2 and an apex opening is opened and closed by the rotation of an inner cap 5 installed inside the apex interior of the barrel as supported by the support. In addition, the inner cap has a protrusion and is resiliently urged in one direction of rotation by a return spring 7, so that the inner cap normally blocks the apex opening. Besides, the inner cap rotates, repulsing the resilient force of the return spring 7, following the actuation of the protrusion to be pressed to the apex of the writing utensil, and as a result, the apex opening of the barrel is opened. Thus, a pen-point can be protruded. Further, with removal of the pressing action applied to the protrusion part of the inner cap by the apex of a writing element, the inner cap makes a reverse rotation by the resilient force of the return spring 7, and blocks the apex opening, forming an airtight space inside the barrel.