Parallel leaf spring, parallel movement mechanism, interference optical system and spectroscopic analysis device

A parallel leaf spring (20) is provided with block bodies (23, 24) that are disposed apart from each other, and two plate-shaped members (21, 22) that are supported by the block body (24) serving as a support and disposed to face each other and sandwich the block body (23) therebetween. The block body (23) constitutes a movable part that reciprocates along the direction in which the two plate-shaped members (21, 22) face each other. The block body (23) as the movable part is formed from a porous material (41).