The present invention relates to a container assembly including a container body for accommodating contents and a cap device detachably installed on the container body, and the cap device includes a first coupling part detachably coupled to the container body and a pass-through device through which the contents accommodated in the container body pass. The cap device includes a holder on which the first coupling part is formed and a cap body including the pass-through device, the holder includes a cylindrical inner wall and a bottom part extending from a bottom of the cylindrical inner wall along an outer circumference thereof, and the first coupling part is formed on an inner circumferential surface of the cylindrical inner wall and screw-coupled to the neck part.