To provide a writing utensil which can securely prevent a plug body from being left out to the rear part of a barrel and also, a projecting member from likewise being left out to the rear part of the barrel.

This writing utensil is structured of a writing utensil body 2 with a pen point 21 which can store an ink internally and discharge the ink, disposed at the forward end, and the rear end part of the writing utensil body 2 is constituted of a cylindrical tube 4. The cylindrical tube 4 has an inner hole opened through in the forward and backward directions, as well as a forward end opening 41 and a rear end opening 42 which communicate with the inner hole. The plug body 5 is forced in and anchored to the inner surface of the cylinder tube 4, and the internal breathing of the cylindrical tube 4 between the forward end opening 41 and the rear end opening 42, is stopped by the plug body 5. Next, the ink is accommodated in the cylindrical tube 4 located forward of the plug body 5. Further, an internal sealing part 43 which is airtightly fitted to the outer surface of the plug body 5, is formed on the inner surface of the cydrindrical tube 4. Besides, regulating wall part 44 which comes into contact with the rear face of the plug body 5 in the forward and backward directions and checks the movement of the plug body 5 to the rear, is formed in one piece, on the inner surface of the cylindrical tube 4 located at the rear of the inner sealing part 43.