An image-forming device, comprising: a medium transport portion that transports media in a medium transport direction; an ink jet printing portion that forms images on the media being transported using ink; a varnish application portion that applies aqueous varnish to the media on which the images are formed; a treatment portion that carries out a heating and drying treatment on the media so that a stickiness evaluation value reaches 0.24 or less which is the stickiness evaluation value indicating a degree of stickiness of the aqueous varnish applied to the media when the media to which the aqueous varnish is applied are output from the varnish application portion and being derived using a damped vibration percentage of a pendulum caused to do pendulum motions from an arbitrary location of the media to which the aqueous varnish is applied as a pivot; and an accumulation portion that accumulates the media to which the aqueous varnish is applied using the varnish application portion and on which the treatment is carried out using the treatment portion, characterized by a first temperature detection portion which is disposed at a location on a downstream side of the printing portion in the medium transport direction and at a location on an upstream side of the varnish application portion in the medium transport direction and detects temperatures of the media on which the images are formed using the printing portion and the aqueous varnish is to be applied using the varnish application portion, wherein the treatment portion includes a drying treatment portion which is disposed at a location on the downstream side of the printing portion in the medium transport direction and at a location on the upstream side of the varnish application portion in the medium transport direction and carries out a drying treatment on the media on which the images are formed using the printing portion and the aqueous varnish is to be applied using the varnish application portion and a drying treatment control portion that controls temperatures of the media on which the drying treatment is carried out using the drying treatment portion by applying drying conditions under which the stickiness evaluation value of the media to which the aqueous varnish is to be applied using the varnish application portion reaches 0.24 or less, and wherein the treatment portion includes a powder spraying portion adapted to spray powder to the media treated using the treatment portion and a powder spraying control portion that sprays powder to the media treated using the treatment portion using the powder spraying portion in a case in which the temperatures of the media detected using the first temperature detection portion are lower than 101°C. a medium transport portion that transports media in a medium transport direction; an ink jet printing portion that forms images on the media being transported using ink; a varnish application portion that applies aqueous varnish to the media on which the images are formed; a treatment portion that carries out a heating and drying treatment on the media so that a stickiness evaluation value reaches 0.24 or less which is the stickiness evaluation value indicating a degree of stickiness of the aqueous varnish applied to the media when the media to which the aqueous varnish is applied are output from the varnish application portion and being derived using a damped vibration percentage of a pendulum caused to do pendulum motions from an arbitrary location of the media to which the aqueous varnish is applied as a pivot; and an accumulation portion that accumulates the media to which the aqueous varnish is applied using the varnish application portion and on which the treatment is carried out using the treatment portion, characterized by a first temperature detection portion which is disposed at a location on a downstream side of the printing portion in the medium transport direction and at a location on an upstream side of the varnish application portion in the medium transport direction and detects temperatures of the media on which the images are formed using the printing portion and the aqueous varnish is to be applied using the varnish application portion, wherein the treatment portion includes a drying treatment portion which is disposed at a location on the downstream side of the printing portion in the medium transport direction and at a location on the upstream side of the varnish application portion in the medium transport direction and carries out a drying treatment on the media on which the images are formed using the printing portion and the aqueous varnish is to be applied using the varnish application portion and a drying treatment control portion that controls temperatures of the media on which the drying treatment is carried out using the drying treatment portion by applying drying conditions under which the stickiness evaluation value of the media to which the aqueous varnish is to be applied using the varnish application portion reaches 0.24 or less, and wherein the treatment portion includes a powder spraying portion adapted to spray powder to the media treated using the treatment portion and a powder spraying control portion that sprays powder to the media treated using the treatment portion using the powder spraying portion in a case in which the temperatures of the media detected using the first temperature detection portion are lower than 101°C.