The purpose of the present invention is to provide a small rotor for a centrifuge, the rotor being configured such that numerous sample containers can be mounted simultaneously and it is easy to take out the sample containers. In an inner peripheral surface 20A of an outer wall part 20, recessed areas 20B locally carved outward are provided in areas between sample container insertion holes 11 that are adjacent to each other in a circumferential direction. In the locations of the recessed areas 20B, the spaces between adjacent sample containers 51 are wider, and the sample containers 51 can easily be taken out.