A half mirror includes, in sequence, a glass plate, an adhesive layer, and a polarized light reflecting layer having a thickness of 5.0 μm or more and 80 μm or less. The adhesive layer has a thickness of 3 μm to 15 μm and is a layer formed by UV-curing of a composition containing an acrylic polymer having a weight-average molecular weight of 800,000 to 2,000,000, a crosslinker, and a silane coupling agent. The total amount of the crosslinker is 1.0 mass % to 8.0 mass % of the amount of the acrylic polymer, and 80 mass % or more of the crosslinker is accounted for by a photo-crosslinker.