To provide a bag with casters capable of being smoothly towed even on rugged places, without causing great impact, to have excellent wheels durability.

A wheel retainer 17 is pivotally attached to a revolving shaft 16, and wheels 20a, 20b, 20c, etc., are mounted to the wheel retainer 17 at three or more positions which are radially and equally spaced apart from the revolving shaft 16, by use of an axle 18 which is parallel to the revolving shaft 16, so as to constitute a revolving wheel body A. A pair of revolving wheel bodies A and A is mounted at a corner portion between the bottom face 32 and the rear face 33 of a bag body B having a handle 31, in such a way that a partial cover body 10 for the wheels is contained in the bag body B.