Abstract: A chair includes a support base body portion; a backrest rotatably supported with respect to the support base body portion on an axis in a width direction of the support base body portion and being displaceable from an initial state to an inclined state of being inclined rearward; a biasing member configured to bias the backrest in the inclined state, in a direction of returning to the initial state; an adjuster configured to adjust a biasing force of the biasing member; and an operating member joined to the adjuster and configured to operate the adjuster, wherein the biasing member is provided in the backrest or the support base body portion, the adjuster is provided in the backrest, and the operating member is disposed behind the axis and on one side of the backrest in the width direction.

Abstract: A load-supporting structure for a chair includes a receiving surface component provided with a curved receiving surface configured to receive a load from a seated person; a load supporter supporting the receiving surface component from a back side of the receiving surface; and a curved shape-changing portion configured to change a curvature radius of the receiving surface from a curvature radius in an initial state thereof to a greater curvature radius than that in the initial state in accordance with a load received by the receiving surface component. The receiving surface component generates a biasing force for returning the curvature radius of the receiving surface to that in the initial state.

Abstract: A chair includes a lower structure configured to be placed on a floor surface (F), a backrest support member supported by the lower structure body, and a backrest supported by the backrest support member. The backrest includes a backrest body fixed to the backrest support member and provided with an opening portion (S2) that opens downward, and a tensile material provided in the backrest body and having a lower end portion that is locked on the backrest body. The backrest body includes a plate-shaped backrest main body fixed to the backrest support member and provided with a load-supporting surface that supports a load of a seated person. The backrest support member is inserted into the opening portion of the backrest body and is disposed on a rear side of the backrest main body.

Abstract: A backrest includes: a backrest body against which a seated person leans a back thereof, a backrest support positioned behind and supporting the backrest body; and an armrest body provided outside in a width direction of the backrest body and supported by the backrest support so as to move up and down at a position separated from the backrest body. A chair includes the above-described backrest.

Abstract: A backrest includes: a backrest body against which a seated person leans a back thereof, a backrest support positioned behind and supporting the backrest body; and an armrest body provided outside in a width direction of the backrest body and supported by the backrest support so as to move up and down at a position separated from the backrest body. A chair includes the above-described backrest.