Unlike a conventional method for evaluating a degree of ultraviolet protection through visual evaluation, the disclosed method for measuring a sunlight protection function can accurately and objectively measure and determine a degree of sunlight protection by measuring a change due to a material to be measured with respect to an expression amount of skin tissue antimicrobial peptides (AMPs) in skin cells, which decrease from exposure to sunlight, and/or a generation amount of S-nitrosylated protein. Additionally, the disclosed measurement method can determine whether blue/violet light of wavelengths of 400-500 nm, which induces the most skin damage among visible rays, is blocked and provide a more specified sunlight protection effect evaluation result. Moreover, by using the disclosed measurement method, a degree of sunlight protection can be indexed, and a sunlight protection composition for protecting normal skin from the blue/violet light can be provided.