Provided are a highly versatile counterfeit-preventive optical element applicable to both the banknote field and the ID field and an information medium including the optical element. A counterfeit-preventive optical element (1) of an embodiment includes a first layer (2), second layer (3), and a third layer (6) that are stacked in this order. A relief structure (R) is provided between the first layer (2) and the second layer (3), the first layer (2) includes a first region (4) and a second region (5), the first region (4) totally reflects incident light incident from the first layer (2) due to at least one of the angle of a face of the relief structure (R) and the refractive index ratio of the first layer (2) and the second layer (3), and the second region (5) transmits or refracts at least some of incident light incident from the first layer (2) due to one of the angle of a face of the relief structure (R) and the refractive index ratio of the first layer (2) and the second layer (3). The transparency of the second region (5) is higher than the transparency of the first region (4) only when the optical element is observed from the first layer (2) at a particular angle.