To easily replace a caster for a bag at low cost without reducing the strength of the caster.

The caster for the bag includes a wheel 10, a wheel attachment plate 20, a bag-side board 30, and the like. The wheel 10 is attached to the wheel attachment plate 20 via an axle 13, a fork part 14, a turning shaft 17, and a bearing 15. The fork part 14 rotatably holds the wheel 10. The wheel attachment plate 20 turnably holds the fork part 14. The bag-side board 30 is fixed to a bag body using four screws 23. A circular central recess 31 which detachably accommodates the wheel attachment plate 20 to support the load is provided in the center of the bag-side board 30. Four screws 22 are provided every 90 degrees on the wheel attachment plate 20. Four female screws 32 are provided every 90 degrees on the central recess 31. The wheel attachment plate 20 is fixed to the bag-side board 30 with the four screws 23 while the wheel attachment plate 20 is fitted to the central recess 31.