A height adjusting device includes an attachment bolt, an adjuster, a female screw portion, and a circular groove. The adjuster includes a flange portion operable from an outside and is fixed to the attachment bolt so as to be rotatable integrally with the attachment bolt. The female screw portion is formed in a piece of furniture. The attachment bolt is screwable into the female screw portion. A circular groove is formed around the female screw portion. The adjuster includes a brake portion protruding from the flange portion in a rotation axis direction of the adjuster. When inserted into the circular groove, the brake portion abuts a wall surface of the circular groove and is at least partially deformed thereby to bias the wall surface, resulting in suppression of rotation of the adjuster.