Lower member fixing device and fluid control device provided with the same

A lower member fixing device, comprising:

• a through hole provided in a lower member, the through hole being formed by a large-diameter section opened in an upper surface and a small-diameter section continued from a lower part of the large-diameter section and opened in a lower surface;
• and
• a fixation member including a shaft section inserted into the small-diameter section of the through hole, a head inserted into the large-diameter section of the through hole, and a magnet section provided at a lower end of the shaft section,
• wherein the fixation member fixes the lower member having the through hole to a support member,
• a diameter of the magnet section is larger than a diameter of the small-diameter section of the through hole,
• at least one slit for enabling reduction in an outer diameter of the head is provided in the head and the shaft section,
• the support member is made of a magnetic substance, and
• a magnetic force applied between the magnet section of the fixation member and the support member prevents the lower member from being separated from the support member.