Abstract: A calcineurin activator, comprising the following protein (a) or (b) as an active ingredient and having the action of increasing intracellular calcium ion concentration through the influx of calcium ions into eukaryotic cells: (a) a killer protein (KLKP), being composed of 3 subunits consisting of amino acid sequences represented by SEQ ID NOS: 2, 3, and 4, respectively, and being produced by Kluyveromyces lactis killer yeast; or (b) a protein, being the same as protein (a) except for differing from protein (a) in that at least one of the 3 subunits consists of an amino acid sequence derived from the amino acid sequence represented by SEQ ID NO: 2, 3, or 4 by deletion, substitution, or addition of 1 or several amino acids, and having Kluyveromyces lactis killer protein (KLKP) activity.