A sample container cap is disclosed. The sample cap container includes a sample cap body capable of covering an opening of a sample container and a centrifugation status indicator device in the top of the sample cap body. The centrifugation status indicator device includes: a first substance having a first density and a first color, and a second substance having a second density and a second color. The centrifugation status indicator device displays the first substance when the sample container has been centrifuged. The first substance can be a gel, and the second substance can include a plurality of particles. The second density is higher than the first density and the second color is different from the first color.