A cap device includes a cap, an accommodation member, and a cover. The cap covers a nozzle surface of a liquid ejection head. The accommodation member is accommodated in the cap and is fixed to the cap. The accommodation member has a conductivity and receives a voltage that generates a potential difference between the liquid ejection head and the accommodation member. The accommodation member includes a first portion and a second portion connected with each other. The cover covers the second portion of the accommodation member, and has a surface that is co-planar with a surface of the first portion. The cover has a conductivity and receives a voltage that generates a potential difference between the liquid ejection head and the cover.