An object of the invention is to provide a gene expression regulating agent which includes astaxanthin and/or its ester as an effective ingredient; and a food and drink having an effect of regulating gene expression which includes astaxanthin and/or its ester. Abnormal gene expression due to, for example, oxidative stress can be treated, improved, and/or prevented, and diseases caused by the abnormal gene expression can be treated, improved, and/or prevented. A gene expression regulating agent which includes astaxanthin and/or its ester as an effective ingredient; and a food and drink having an effect of regulating gene expression which includes astaxanthin and/or its ester are provided and are useful for treating, improving, and/or preventing the symptom caused by the abnormal gene expression, that is, excessive expression or suppression of expression.