An inkjet printer including a printhead unit. The printhead unit includes a printhead for ejecting ink onto a sheet and a plurality of sub-tanks for supplying the ink to the printhead. The printhead unit is configured to reciprocate in a main scanning direction that is perpendicular to a sheet conveying direction. The plurality of sub-tanks is arranged such that two of the plurality of sub-tanks are adjacent to each other. The adjacent two sub-tanks overlap with each other, at least partially, both as seen in a direction parallel to the main scanning direction and as seen in a direction parallel to the sheet conveying direction.