This invention provides a novel transformed cell useful in constructing an anti-aging agent screening system, a screening method which uses the same and an anti-aging agent, and it relates to a transformed cell in which a gene coding for (a) a protein capable of phosphorylating p38 protein, or (b) p38 protein, a mutant of p38 protein, a kinase domain of p38 protein, a kinase domain of p38 protein mutant or a fusion protein containing them is transformed into a normal cell, a screening method which uses this transformed cell and an anti-aging agent which uses a compound obtained by the screening method as the active ingredient.