A genetic polymorphism and a hair shape susceptibility gene that are related to hair shape, and a method for determining the genetic susceptibility to hair shape in individual test subjects are provided. Disclosed is a hair shape susceptibility gene, which overlaps with a haplotype block in 1q21.3 region (D1S2696 to D1S2346) of human chromosome 1 and comprises a portion or the entirety of the base sequence of the haplotype block, wherein the haplotype block is determined by a linkage disequilibrium analysis conducted on a single nucleotide polymorphism (SNP) marker whose allele frequency differs statistically significantly between a group having a curly hair trait and a group having a non-curly hair trait, and consists of a base sequence set forth in any one of SEQ ID NO: 1 to NO: 5.