To provide a rodless cylinder device capable of improving driving force, having excellent durability, and interchangeably usable for linear transfers of various kinds of physical distributions at industrial sites and transfers for light cargo and heavy cargo.

This rodless cylinder device has a movable member 22, a cylinder 6, a piston 7, a cylinder cap 8, a chain 200 for connecting the piston 7 and the movable member 22, and a sprocket 100 for guiding the chain 200, and drives the movable member 22 by supplying compressed air to one of cylinder chambers 6a and 6b of the cylinder 6. The chain 200 is made of link members 300. The link member 300 has a shaft part 40 and connecting parts 50 and 60. The connecting part 50 and the connecting part 60 are hinge connected with each other. The sprocket 100 has supporting surfaces 110 disposed according to the intervals of the link members 300 and is constituted of a plurality of recessed parts 120 fitted with the shaft part 40 therein.