A belt adjusting and holding device includes: a device body including a belt insertion part allowing insertion of a belt and an opening section communicating with the belt insertion part; and a belt folding member including a grasping part and a folding-back part to fold back the belt within the opening section. The belt folding-back member is configured to move forward and backward within the device body. Standing wall portions rising in a stepped shape are formed on the upper and lower inner wall surfaces of the belt insertion part. The belt folding-back member is formed with a protrusion, which substantially stepwisely bends the belt between the protrusions and the standing wall portions at a backward position of the belt folding-back member and release the belt at a forward position of the belt folding member.