A posture adjusting device includes a support member with a pressure receiving surface to be pressed by a body of a user, multiple posture adjusting members each configured to change an uneven state of the pressure receiving surface, a sensor configured to output, when a given posture adjusting member is pressed by the body via the pressure receiving surface, a resistance value that constantly varies in accordance with a magnitude of a press force that is transferred via the given posture adjusting member, a drive unit configured to independently drive each of the multiple posture adjusting members, and a control unit configured to identify the pressed posture adjusting member based on the output of the sensor, and to control the drive unit to cause the pressed posture adjusting member to be moved or deformed to thereby cause the uneven state of the pressure receiving surface to change.