PROBLEM TO BE SOLVED: To provide materials, such as food, pharmaceuticals, and cosmetics, having an anti-endoplasmic reticulum stress effect, and useful for circadian rhythm control.SOLUTION: The present invention provides: an anti-endoplasmic reticulum stress agent and a circadian rhythm control agent, containing 5-hydroxy-4-phenylbutenolide or a salt thereof as an active ingredient and an anti-endoplasmic reticulum stress composition and a circadian rhythm control composition, containing 5-hydroxy-4-phenylbutenolide or a salt thereof.SELECTED DRAWING: NoneCOPYRIGHT: (C)2018,JPO&INPIT【課題】抗小胞体ストレス、概日リズム調整に有用な食品、医薬品、化粧品などの材料を提供する。【解決手段】5-ヒドロキシ-4-フェニルブテノライド又はその塩を有効成分として含む抗小胞体ストレス剤、概日リズム調整剤、並びに、5-ヒドロキシ-4-フェニルブテノライド又はその塩を含む抗小胞体ストレス用組成物、概日リズム調整用組成物。【選択図】なし