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 the 1q32.1 to 1q32.2 region (D1S249 to D1S2891) 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:3.