A necklace has an adjustable loop size so that anyone having a thick or a slender neck can wear a necklace of one size so which is adjustable that it fits the wearer best. A hook formed by bending a material is provided at an end of the string necklace, formed by connecting pearls together with a string. A loop is formed by engaging the hook in a valley portion between any adjacent pearls. By engaging the hook in different valleys, it is possible to change the size of the necklace loop freely, so that it is possible to form a loop of the best size for each wearer.