A head unit configured to be detachably arrayed in a predetermined array direction on a base member extending lengthwise in the array direction, each head unit comprising: an ink discharge head having a nozzle surface configured to discharge an ink; a head holder attachable to and detachable from the base member while holding the ink discharge head in a holding region; the head holder including a first holder member provided on one side of the holding region and a second holder member provided on the other side of the holding region in the array direction, wherein the holding region is located between the first holder member and the second holder member and extends along a surface normal to the nozzle surface; a posture adjustment mechanism configured to adjust a posture of the nozzle surface with respect to the head holder, which is to be attached to the base member, by rotating the ink discharge head with respect to the head holder about an axis of rotation perpendicular to both the surface normal to the nozzle surface and the array direction in a state where the head holder is not attached to the base member, the posture adjustment mechanism including: a first movable member and a second movable member provided movably back and forth from and to the holding region with respect to the first holder member, the first and second movable members (641, 642) coming into contact with the ink discharge head located in the holding region by projecting into the holding region; and a third movable member provided movably back and forth from and to the holding region with respect to the second holder member while facing an intermediate part of the first holder member located between the first and second movable members (641,641), the third movable member coming into contact with the ink discharge head located in the holding region by projecting into the holding region, and a rotation amount of the ink discharge head about the axis of rotation is adjusted as a projection amount of one of the first and second movable members (641, 641) into the holding region is increased and a projection amount of the other into the holding region is reduced. an ink discharge head having a nozzle surface configured to discharge an ink; a head holder attachable to and detachable from the base member while holding the ink discharge head in a holding region; the head holder including a first holder member provided on one side of the holding region and a second holder member provided on the other side of the holding region in the array direction, wherein the holding region is located between the first holder member and the second holder member and extends along a surface normal to the nozzle surface; a posture adjustment mechanism configured to adjust a posture of the nozzle surface with respect to the head holder, which is to be attached to the base member, by rotating the ink discharge head with respect to the head holder about an axis of rotation perpendicular to both the surface normal to the nozzle surface and the array direction in a state where the head holder is not attached to the base member, the posture adjustment mechanism including: a first movable member and a second movable member provided movably back and forth from and to the holding region with respect to the first holder member, the first and second movable members (641, 642) coming into contact with the ink discharge head located in the holding region by projecting into the holding region; and a third movable member provided movably back and forth from and to the holding region with respect to the second holder member while facing an intermediate part of the first holder member located between the first and second movable members (641,641), the third movable member coming into contact with the ink discharge head located in the holding region by projecting into the holding region, and a first movable member and a second movable member provided movably back and forth from and to the holding region with respect to the first holder member, the first and second movable members (641, 642) coming into contact with the ink discharge head located in the holding region by projecting into the holding region; and a third movable member provided movably back and forth from and to the holding region with respect to the second holder member while facing an intermediate part of the first holder member located between the first and second movable members (641,641), the third movable member coming into contact with the ink discharge head located in the holding region by projecting into the holding region, and a rotation amount of the ink discharge head about the axis of rotation is adjusted as a projection amount of one of the first and second movable members (641, 641) into the holding region is increased and a projection amount of the other into the holding region is reduced.