The present invention relates to a method for preparing a plasma for preventing or treating a cancer. Also, the present invention relates to a liquid type plasma for preventing or treating a cancer prepared by treating the plasma and a pharmaceutical composition for preventing or treating a cancer comprising the same. The plasma and the liquid type plasma according to the present invention can effectively induce cancer cell death without a surgical operation or in a treatment process after a surgical operation, thereby being useful as a novel therapeutic agent and method for a cancer.