An inkjet printer for preventing ink flow, color blurring and color mixing during multicolor printing when image formation is performed with aqueous ink on a web-shaped printing base material, and an inkjet printing method using the inkjet printer. The inkjet printer is configured to perform image formation by discharging aqueous ink to a web-shaped printing base material, and includes: a conveyance mechanism configured to continuously convey the web-shaped printing base material; a single-pass system inkjet head configured to discharge the aqueous ink to a surface of the web-shaped printing base material conveyed by the conveyance mechanism; and a surface pre-heating unit arranged on an upstream side of conveyance from the single-pass system inkjet head and configured to heat at least the surface of the web-shaped printing base material. Image formation is performed on the web-shaped printing base material heated by the surface pre-heating unit.