A container (1A; 1B) for testing blood comprising: a main container body having an internal space that stores an initial blood flow to be used for a test; a blood inflow port that communicates with the internal space and allows the initial blood flow to inflow; a blood outflow port that communicates with the internal space and allows the stored initial blood flow to outflow; a blood drawing part that is connected to the blood outflow port and allows the initial blood flow to be drawn; and a first discharge part that communicates with the internal space, has a hydrophilic bacteria-impermeable first filter, and discharges air in the internal space, whereby the first discharge part and the blood outflow port are disposed at an end part of the main container body on the same side, and the blood drawing part connected to the blood outflow port includes: a needle assembly having a hollow needle that communicates with the blood outflow port; and a cylindrical holder whose one end is provided with the needle assembly and whose other end has an opening in which a testing instrument storing the initial blood flow is inserted, characterized in that while the container (1A; 1B) for testing blood is in an horizontally placed state in which the whole of the container (1A; 1B) for testing blood is placed horizontally so that a surface of the container (1A; 1B) for testing blood is in contact with a work table or the like, the blood outflow port is disposed at a higher position than the blood inflow port. a main container body having an internal space that stores an initial blood flow to be used for a test; a blood inflow port that communicates with the internal space and allows the initial blood flow to inflow; a blood outflow port that communicates with the internal space and allows the stored initial blood flow to outflow; a blood drawing part that is connected to the blood outflow port and allows the initial blood flow to be drawn; and a first discharge part that communicates with the internal space, has a hydrophilic bacteria-impermeable first filter, and discharges air in the internal space, whereby the first discharge part and the blood outflow port are disposed at an end part of the main container body on the same side, and the blood drawing part connected to the blood outflow port includes: a needle assembly having a hollow needle that communicates with the blood outflow port; and a cylindrical holder whose one end is provided with the needle assembly and whose other end has an opening in which a testing instrument storing the initial blood flow is inserted, a needle assembly having a hollow needle that communicates with the blood outflow port; and a cylindrical holder whose one end is provided with the needle assembly and whose other end has an opening in which a testing instrument storing the initial blood flow is inserted, characterized in that while the container (1A; 1B) for testing blood is in an horizontally placed state in which the whole of the container (1A; 1B) for testing blood is placed horizontally so that a surface of the container (1A; 1B) for testing blood is in contact with a work table or the like, the blood outflow port is disposed at a higher position than the blood inflow port.