An inkjet printer for both surface printing and back printing, which is for performing both of surface printing and back printing by discharging aqueous inks on a web-shaped print base material by a single-pass method, the inkjet printer comprising: a conveyance mechanism configured to perform continuous conveyance of the web-shaped print base material; a first white inkjet head configured to discharge a white aqueous ink by a single-pass method to a surface of the web-shaped print base material conveyed by the conveyance mechanism in a case of surface printing; a first drum-type drying unit configured to dry the white aqueous ink discharged by the first white inkjet head in the case of surface printing; a single-pass inkjet head configured to discharge a non-white aqueous ink to a surface of the web-shaped print base material conveyed by the conveyance mechanism in the case of surface printing and in a case of back printing; a second white inkjet head configured to discharge a white aqueous ink by a single-pass method to a surface of the web-shaped print base material conveyed by the conveyance mechanism in the case of back printing; a second drum-type drying unit configured to dry the white aqueous ink discharged by the second white inkjet head in the case of back printing; and surface heating portions (70a, 70b, 70c, 70d, 70e, 70f) configured to heat at least the surface of the web-shaped print base material, which provided downstream of each of the first white inkjet head, the single-pass inkjet head and the second white inkjet head, wherein each droplet amount of the first white inkjet head and the second white inkjet head are larger than each droplet amount of the single-pass inkjet head (24a, 24b, 24c, 24d) for the non-white aqueous inks, wherein the white aqueous ink has a solid content and a viscosity higher than those of the non-white aqueous inks, wherein the first drum-type drying unit and the second drum-type drying unit are each a drum-type drying unit including: a housing having a heat-insulation structure with an inlet and an outlet for the web-shaped print base material; a drum body installed inside the housing; and a heating mechanism configured to heat an inside of the housing, and wherein the first drum-type drying unit and the second drum-type drying unit are each configured to dry the white aqueous ink while the web-shaped print base material is conveyed on a peripheral surface of the drum body. a conveyance mechanism configured to perform continuous conveyance of the web-shaped print base material; a first white inkjet head configured to discharge a white aqueous ink by a single-pass method to a surface of the web-shaped print base material conveyed by the conveyance mechanism in a case of surface printing; a first drum-type drying unit configured to dry the white aqueous ink discharged by the first white inkjet head in the case of surface printing; a single-pass inkjet head configured to discharge a non-white aqueous ink to a surface of the web-shaped print base material conveyed by the conveyance mechanism in the case of surface printing and in a case of back printing; a second white inkjet head configured to discharge a white aqueous ink by a single-pass method to a surface of the web-shaped print base material conveyed by the conveyance mechanism in the case of back printing; a second drum-type drying unit configured to dry the white aqueous ink discharged by the second white inkjet head in the case of back printing; and surface heating portions (70a, 70b, 70c, 70d, 70e, 70f) configured to heat at least the surface of the web-shaped print base material, which provided downstream of each of the first white inkjet head, the single-pass inkjet head and the second white inkjet head, wherein each droplet amount of the first white inkjet head and the second white inkjet head are larger than each droplet amount of the single-pass inkjet head (24a, 24b, 24c, 24d) for the non-white aqueous inks, wherein the white aqueous ink has a solid content and a viscosity higher than those of the non-white aqueous inks, wherein the first drum-type drying unit and the second drum-type drying unit are each a drum-type drying unit including: a housing having a heat-insulation structure with an inlet and an outlet for the web-shaped print base material; a drum body installed inside the housing; and a heating mechanism configured to heat an inside of the housing, and wherein the first drum-type drying unit and the second drum-type drying unit are each configured to dry the white aqueous ink while the web-shaped print base material is conveyed on a peripheral surface of the drum body. a housing having a heat-insulation structure with an inlet and an outlet for the web-shaped print base material; a drum body installed inside the housing; and a heating mechanism configured to heat an inside of the housing, and wherein the first drum-type drying unit and the second drum-type drying unit are each configured to dry the white aqueous ink while the web-shaped print base material is conveyed on a peripheral surface of the drum body.