Provided is a method for culturing cells, which prevents the possibility of mycoplasma contamination by culturing the cells using biomass extract obtained by culturing a strain with amphidinol productivity, preferably a strain such as Amphidinium klebsii, Amphididinium carterae, and the like belonging to Dinoflagellates, or using a fraction obtained from the extract; and a method for removing mycoplasma contamination of the cells by culturing the cells contaminated by mycoplasma using the amphidinol derivatives. In addition, provided is a method for removing mycoplasma contamination of the cells, including a combination of single cell-isolating enzyme solution treatment and cell aggregate removal.