The invention provides a photopolymerizable composition comprising: flame-retardant particles which contains a hydrated metal and have an average diameter of about 1 to 500 nm; and a photopolymerization reactive material. The hydrated metal preferably includes at least one selected from the group consisting of a hydrated magnesium, hydrated calcium, hydrated aluminum, hydrated zinc, hydrated barium, hydrated copper and hydrated nickel. A cover layer which comprises an organic compound or a polysilicone is preferably formed on surfaces of the flame-retardant particles. The invention provides a flame-retardant resin-formed article which is formed of the photopolymerized photopolymerizable composition. A flame retardancy of the article measured in accordance with the UL-94 test preferably scores HB or higher.