To provide a core pipe structure of stencil base paper roll that has a simple structure, is inexpensive, and can certainly prevent mounting error, and a holder adapting to this core pipe.

In a core pipe of stencil base paper roll R whose both ends are provided with holders H, H" having a guide plate 21, the both ends are provided with openings 14, 16 inserted with projections 22, 23 projecting from the guide plate, the both openings have mutually different inside measure sizes, projections 22, 23 with different sizes are inserted. The core pipe comprises a first pipe body 11, the opening 14 is one end opening of the pipe body 11, and the opening 16 is the opening 16 of a second pipe body 15 spectroscopically arranged adjacent to the other end opening of the pipe body 11. The pipe body 15 is placed inside a prescribed distance away from an end of the pipe body 11 to define a step portion 17, and the holder H" is provided with a shoulder portion 24 stored in this step portion 17.