A rolling device including an axle rotatable about an axis, and a wheel body disposed around the axle, wherein the wheel body includes: a plurality of first rolling members connected fixedly to the axle and angularly spaced apart from each other, each of the first rolling members including a first body having a first rolling surface that is contactable with the ground surface and that is spaced apart from the axis by a first radius, any two adjacent ones of the first rolling members defining an accommodating space therebetween; and a plurality of second rolling members each disposed movably within the accommodating space between two adjacent ones of the first rolling members, each of the second rolling members including a second body having a second rolling surface that is contactable with the ground surface and that is spaced apart from the axis by a second radius, each of the second rolling members being movable relative to the first rolling members between a retracted position whereat the second radius is not more than the first radius, and an extended position whereat the second radius is more than the first radius; the rolling device further including a plurality of reinforcing units each connected between two adjacent ones of the first rolling members; wherein each of the reinforcing units includes two reinforcing walls connected respectively to two opposite sides of each of two adjacent ones of the first rolling members; wherein each of the second rolling members further includes a first positioning mechanism disposed at the second body, each of the reinforcing units further including a second positioning mechanism disposed on the two reinforcing walls and cooperating with the first positioning mechanism of a corresponding one of the second rolling members to maintain a corresponding one of the second rolling members at a selected one of the retracted position and the extended position; and the rolling device being characterized in that: the first positioning mechanism of each of the second rolling members includes a plurality of positioning holes formed through the second body of a corresponding one of the second rolling members, and the second positioning mechanism of each of the reinforcing units includes a plurality of positioning pins each extending through a corresponding one of the positioning holes and two corresponding ones of the reinforcing walls. a plurality of first rolling members connected fixedly to the axle and angularly spaced apart from each other, each of the first rolling members including a first body having a first rolling surface that is contactable with the ground surface and that is spaced apart from the axis by a first radius, any two adjacent ones of the first rolling members defining an accommodating space therebetween; and a plurality of second rolling members each disposed movably within the accommodating space between two adjacent ones of the first rolling members, each of the second rolling members including a second body having a second rolling surface that is contactable with the ground surface and that is spaced apart from the axis by a second radius, each of the second rolling members being movable relative to the first rolling members between a retracted position whereat the second radius is not more than the first radius, and an extended position whereat the second radius is more than the first radius; the rolling device further including a plurality of reinforcing units each connected between two adjacent ones of the first rolling members; wherein each of the reinforcing units includes two reinforcing walls connected respectively to two opposite sides of each of two adjacent ones of the first rolling members; wherein each of the second rolling members further includes a first positioning mechanism disposed at the second body, each of the reinforcing units further including a second positioning mechanism disposed on the two reinforcing walls and cooperating with the first positioning mechanism of a corresponding one of the second rolling members to maintain a corresponding one of the second rolling members at a selected one of the retracted position and the extended position; and the rolling device being characterized in that: the first positioning mechanism of each of the second rolling members includes a plurality of positioning holes formed through the second body of a corresponding one of the second rolling members, and the second positioning mechanism of each of the reinforcing units includes a plurality of positioning pins each extending through a corresponding one of the positioning holes and two corresponding ones of the reinforcing walls. the first positioning mechanism of each of the second rolling members includes a plurality of positioning holes formed through the second body of a corresponding one of the second rolling members, and the second positioning mechanism of each of the reinforcing units includes a plurality of positioning pins each extending through a corresponding one of the positioning holes and two corresponding ones of the reinforcing walls.