Fixing device for lower stage members and fluid control device equipped with fixing device

A fixing device for a lower-stage member which fixes the lower-stage member arranged between a support member and an upper-stage member and provided with a bolt insertion hole to a support member by a bolt, wherein the bolt insertion hole formed in the lower-stage member is formed of a large-diameter portion having a diameter larger than a diameter of a bolt head portion and a small-diameter portion which is contiguously formed with the large-diameter portion below the large-diameter portion by way of a stepped portion and has an intermediate diameter between the diameter of the bolt head portion and a diameter of a bolt shaft portion, a cylindrical spacer which has an inner diameter larger than the diameter of the bolt shaft portion and has a lower end thereof received by the support member and an upper end thereof disposed in the inside of the large-diameter portion is fitted into the small-diameter portion of the bolt insertion hole, and an elastic member which biases the lower-stage member toward the support member is interposed between the bolt head portion and the stepped portion, wherein

• a cutout which allows the elastic member to be elastically deformed by bending when a force in the vertical direction is applied to the elastic member is formed at at least one place among an outer peripheral surface, an inner peripheral surface, an upper surface and a lower surface of the elastic member.