Provided are an inkjet printer and an inkjet printing method with which, when image forming is performed on a web-shaped printing base material with inkjet inks, nozzles for discharging the inks are less liable to clog, streaks or density unevenness is less liable to occur at the time of solid printing, and a density of a single-color printing portion is easily increased. The inkjet printer for an inkjet ink is configured to perform image forming by discharging inkjet inks on a web-shaped printing base material by a single-pass method. The inkjet printer includes: a conveyance mechanism configured to continuously convey the web-shaped printing base material; a plurality of single-pass inkjet heads configured to discharge the inkjet inks to a front surface of the web-shaped printing base material conveyed by the conveyance mechanism; and a curing device configured to cure the inkjet inks discharged on the front surface of the web-shaped printing base material. Resolutions of the plurality of single-pass inkjet heads are varied depending on colors of the inkjet inks.