A tube rack of a centrifugal separator, comprising: a holder including a plurality of tube holes each configured to accommodate a tube that is used for a sample, and the plurality of tube holes each includes an opening at one end portion of the holder serving as a tube insertion side and an opening at a bottom portion of the holder that is at the other end; a base formed in a cylindrical shape that has a bottom configured to accommodate and detachably hold the holder, and to be inserted into a bucket of the centrifugal separator, characterized by a bottom rubber main body including a plurality of bottom rubber members each fits in the opening of the bottom portion of each of the plurality of tube holes, and including connecting portions each configured to connect the plurality of bottom rubber members that are adjacent to each other; wherein the bottom is configured to accommodate and detachably hold the bottom rubber main body, wherein each of the plurality of bottom rubber members is formed in a columnar shape in which a distal end surface oriented to the opening of the tube insertion side of the tube hole is located at one end in an axial direction, each of the connecting portions is part of an outer surface of each of the plurality of bottom rubber members, and is projected outward in a radial direction from a portion that is located in the vicinity of a bottom surface formed on an opposite side of the distal end surface, in the axial direction of the each of the plurality of bottom rubber members, and a notch configured to accommodate the each of the connecting portions formed in a portion that is the bottom portion of the holder serving as a hole wall of the each of the plurality of tube holes. a holder including a plurality of tube holes each configured to accommodate a tube that is used for a sample, and the plurality of tube holes each includes an opening at one end portion of the holder serving as a tube insertion side and an opening at a bottom portion of the holder that is at the other end; a base formed in a cylindrical shape that has a bottom configured to accommodate and detachably hold the holder, and to be inserted into a bucket of the centrifugal separator, characterized by a bottom rubber main body including a plurality of bottom rubber members each fits in the opening of the bottom portion of each of the plurality of tube holes, and including connecting portions each configured to connect the plurality of bottom rubber members that are adjacent to each other; wherein the bottom is configured to accommodate and detachably hold the bottom rubber main body, wherein each of the plurality of bottom rubber members is formed in a columnar shape in which a distal end surface oriented to the opening of the tube insertion side of the tube hole is located at one end in an axial direction, each of the connecting portions is part of an outer surface of each of the plurality of bottom rubber members, and is projected outward in a radial direction from a portion that is located in the vicinity of a bottom surface formed on an opposite side of the distal end surface, in the axial direction of the each of the plurality of bottom rubber members, and a notch configured to accommodate the each of the connecting portions formed in a portion that is the bottom portion of the holder serving as a hole wall of the each of the plurality of tube holes.