PROBLEM TO BE SOLVED: To provide a hydraulic pressure actuator capable of sufficiently reducing a diameter, and capable of exhibiting sufficient driving force and durability.SOLUTION: A hydraulic pressure actuator 300 includes an inner tube 310 expanded/contracted by supply/discharge of fluid, and a mesh sleeve 330 covering an outer periphery of the inner tube 310 so that as a diameter is increased with expansion of the inner tube 310, a length is contracted. The inner tube 330 has a relatively thick region and a relatively thin region in a cross section thereof. Alternatively, the inner tube 310 has a region formed of a relatively high hardness material and a region formed of a relatively low hardness material in the cross section.
