To provide a linear cylinder device capable of reducing axial direction space, dispensing with a hydraulic pump, and easily controlling rod speed and pressure.

This linear cylinder device 10 is provided with a first cylinder 16a provide with a first piston 16, and an reciprocal mechanism 20 for the first piston 16. The reciprocal mechanism 20 is disposed through the first piston 16, and it comprises a rotary rod 12 having a circular cross section to be connectable to a rotation drive source, a plurality of roller bearings 21 and 22 to which a protruded ring 25 formed inside inner rings 23 and 24 is inscribed at a specified rotation angle α to an outer circumference of the rotary rod 12, and a support frame 32 disposed to support outer rings 49 and 49a of the roller bearings 21 and 22. As the rotary rod 12 is rotated, the first piston 16 moves linearly along the rotary rod 12.