To realize the portability of writing utensil having various thicknesses and lengths.

A guide rail 44 is fixed along the X-direction on the cover side edge part 20 of a system pocketbook 10. A holding member 30 is provided integrally with a slider 42 sliding on the guide rail 44. An annular member 50 for controlling the peripheral length of the cylindrical part 32 of the holding member 30 is provided. By controlling the peripheral length of the cylindrical part 32 in response to the thickness of a writing utensil 22, the writing utensil 22 is close-contactingly held in the cylindrical part 32. By controlling the engaging position of the holding member 30 in the X-direction in response to the length of the writing utensil 22, the writing utensil 22 is housed in the system pocketbook 10.