To provide a volume reduction device capable of making a device structure compact, reducing manufacturing cost, and completely volume-reducing any objects to be processed.

The volume reduction device 3 is provided with: a first opposite member 50; a second opposite member 51 which is placed opposite to the first opposite member 50 with some gap and freely moves in parallel in the direction approaching/separating from the first opposite member 50; a holding mechanism part for holding an object T to be processed between the first opposite member 50 and the second opposite member 51; a guiding mechanism part 80 for guiding the parallel movement of the second opposite member 51; and a drive mechanism part 65 for moving the second opposite member 51 in the direction approaching/separating from the first opposite member 50. The guiding mechanism part 80 guides the second opposite member 51 in the oblique direction where a movement component in the opposite direction to the first opposite member 50 and a movement component in the direction orthogonal to the opposite direction are synthesized when the second opposite member 51 approaches the first opposite member 50.