A service tank (100,101,102) used in an inkjet printing apparatus and for temporarily storing ink (2a,2as,2at) introduced from an ink tank and directly supplying the ink (2a,2as,2at) to a printing unit (20a,20as,20at) in a case where a liquid surface of the ink (2a,2as,2at) is in a proper area between an upper limit and a lower limit, the service tank (100,101,102) comprising: a container (10,10s,10t) having an internal space (1, 1s, 1t) in which the ink (2a,2as,2at) is able to be stored, the container (10,10s,10t) being provided with an inlet (11,11s,11t) through which the ink (2a,2as,2at) is introduced into the internal space (1,1s, 1t) and a plurality of supply ports (12, 12s, 12t) for supplying the ink (2a,2as,2at) stored in the internal space (1,1s,1t) to each of a plurality of the printing units (20a,20as,20at); a divider (30,30s,30t) attached to the container (10,10s,10t) and configured to divide the internal space (1,1s,1t) into a plurality of compartments (30a,30as,30at) with a vertical surface; an auxiliary divider having a U shape in top view, the auxiliary divider being attached directly above one of the supply ports (12,12s,12t) and composed of a basal portion, a left small piece provided on a left of the basal portion, and a right small piece provided at a right of the basal portion; and a detector (60,60s,60t) provided in the container (10,10s,10t) and configured to detect that the liquid surface of the ink (2a,2as,2at) stored in the internal space (1,1s, 1t) is at the upper limit or the lower limit, wherein the divider (30,30s,30t) is attached to the container (10,10s,10t) between the inlet (11,11s,11t) and one of the supply ports (12,12s,12t) provided next to the inlet (11,11s,11t), the divider (30,30s,30t) comprises of a plate for blocking flow of the ink (2a,2as,2at) and air above the ink (2a,2as,2at) between adjacent ones of the compartments (30a,30as,30at), an opening for ink (32a1) through which the ink (2a,2as,2at) flows between the adjacent compartments, an auxiliary opening for ink (32a2) through which the ink (2a,2as,2at) flows between the adjacent compartments, and an opening for air through which the air flows between the adjacent compartments, in the divider (30,30s,30t), only the plate from a group consisting of the plate, the opening for ink (32a1), the opening for air, and the auxiliary opening for ink (32a2), is located in the proper area, the opening for ink (32a1) is located in the ink (2a,2as,2at), and provided either in a middle portion of the divider (30,30s,30t) between upper and lower sides of a portion of the divider (30,30s,30t) that is immersed in the ink (2a,2as,2at) in a case where the liquid surface of the ink (2a,2as,2at) stored is at the lower limit or above the middle portion, and the auxiliary opening for ink (32a2) is provided at a lower level than the opening for ink (32a1). the opening for air is located above the ink (2a,2as,2at); the supply port (12,12s,12t) is located between the left small piece and the right small piece in top view. a container (10,10s,10t) having an internal space (1, 1s, 1t) in which the ink (2a,2as,2at) is able to be stored, the container (10,10s,10t) being provided with an inlet (11,11s,11t) through which the ink (2a,2as,2at) is introduced into the internal space (1,1s, 1t) and a plurality of supply ports (12, 12s, 12t) for supplying the ink (2a,2as,2at) stored in the internal space (1,1s,1t) to each of a plurality of the printing units (20a,20as,20at); a divider (30,30s,30t) attached to the container (10,10s,10t) and configured to divide the internal space (1,1s,1t) into a plurality of compartments (30a,30as,30at) with a vertical surface; an auxiliary divider having a U shape in top view, the auxiliary divider being attached directly above one of the supply ports (12,12s,12t) and composed of a basal portion, a left small piece provided on a left of the basal portion, and a right small piece provided at a right of the basal portion; and a detector (60,60s,60t) provided in the container (10,10s,10t) and configured to detect that the liquid surface of the ink (2a,2as,2at) stored in the internal space (1,1s, 1t) is at the upper limit or the lower limit, wherein the divider (30,30s,30t) is attached to the container (10,10s,10t) between the inlet (11,11s,11t) and one of the supply ports (12,12s,12t) provided next to the inlet (11,11s,11t), the divider (30,30s,30t) comprises of a plate for blocking flow of the ink (2a,2as,2at) and air above the ink (2a,2as,2at) between adjacent ones of the compartments (30a,30as,30at), an opening for ink (32a1) through which the ink (2a,2as,2at) flows between the adjacent compartments, an auxiliary opening for ink (32a2) through which the ink (2a,2as,2at) flows between the adjacent compartments, and an opening for air through which the air flows between the adjacent compartments, in the divider (30,30s,30t), only the plate from a group consisting of the plate, the opening for ink (32a1), the opening for air, and the auxiliary opening for ink (32a2), is located in the proper area, the opening for ink (32a1) is located in the ink (2a,2as,2at), and provided either in a middle portion of the divider (30,30s,30t) between upper and lower sides of a portion of the divider (30,30s,30t) that is immersed in the ink (2a,2as,2at) in a case where the liquid surface of the ink (2a,2as,2at) stored is at the lower limit or above the middle portion, and the auxiliary opening for ink (32a2) is provided at a lower level than the opening for ink (32a1). the opening for air is located above the ink (2a,2as,2at); the supply port (12,12s,12t) is located between the left small piece and the right small piece in top view.