To provide the mechanism of a new bi-directional actuation cylinder device that can lower pump capacity, shorten a working time, save energy, and increase workability sharply.

This cylinder device comprises fixed tables 13, 14, and a movable cylinder member 20. The fixed tables 13, 14 are set facing to each other on the both ends of a connection rod 11 in the axial direction. The movable cylinder member 20 is inserted by the connection rod between the tables. Furthermore, the cylinder member 20 has outer cylinder parts 21 and an inner cylinder part 31. The outer cylinder part, fitly inserted by an outer piston 22 that is firmly fixed with the connection rod, has an outer front side inflow part 25, an outer rear side inflow part 26, an outer front side outflow part 27, and an outer rear side outflow part 28. The inner cylinder part, fitly inserted by an inner piston 32 that has working members 33, 34 integrally, has an inner rear side inflow part 35 and an inner front side inflow part 36.