PROBLEM TO BE SOLVED: To provide a linear drive device capable of performing a linear motion by a balloon drive part to be expanded by air supply.SOLUTION: A linear drive device includes a conversion part 30 for outputting the expansion motion of a balloon drive part 20 as a motion in a linear direction. The balloon drive part 20 includes: a base part 21 arranged along a surface parallel with the linear direction a first film body 24 to be expanded by the pressure of air supplied between itself and the base part 21 and a second film body 25 to be expanded by the pressure of air supplied between itself and the base part 21. The conversion part 30 is arranged by enclosing the balloon drive part 20 from the side of the first film body 24 and the side of the second film body 25, is deformable by following the expansion motions of the first film body 24 and the second film body 25, and performs a shortening motion in a direction parallel with the surface when expanded in a direction orthogonally crossed with the surface by the expansion motion.
