A volatilization device (10) according to the present invention comprises: an annularly continuous circumferential wall (22) that is fitted to the edge of an opening of a container (1) which has a volatile chemical agent housed therein； a top wall (24) that has volatilization holes (21), is continuous with one axial end of the circumferential wall, and faces the opening； and slits (26) disposed between the circumferential wall and the top wall.
