A holder that is detachably attachable to a casing of a communication apparatus, including: a placement surface on which a handset can be placed; a first side surface; a displacement unit that is displaced in response to an act of placing the handset on the placement surface; a lever that is displaced according to a displacement of the displacement unit, the lever being projected in a first direction by a first distance from the first side surface; and an engagement portion being projected substantially in the first direction by a second distance, which is longer than the first distance, from the first side surface, the engagement portion engaging the holder with the casing.