A fracture determination method for determining a fracture of a metal structure, the method comprising: a deformation analyzing step (S21, S22, S23) of performing deformation analysis from start of deformation to end of deformation of the metal structure; a fracture determination step (S24, S25, S26) of extracting a fracture determination target portion from a deformation state of the metal structure obtained in the deformation analyzing step (S21, S22, S23), and when the extracted fracture determination target portion has returned from a plastic state to an elastic state, given that a stress when the portion returned to the elastic state is (x, y) = (σ2, σ1) (maximum principal stress: σ1, minimum principal stress: σ2) on a (x, y) coordinate plane, and performing fracture determination of the fracture determination target portion using a re-yield stress determined by an intersection between a straight line satisfying a relation y = (σ1/σ2)x and an yield curve obtained from the plastic state of the fracture determination target portion, wherein, in the fracture determination step (S24, S25, S26), a fracture limit stress determined by an intersection between the straight line satisfying the relation y = (σ1/σ2)x and a fracture limit stress line of the fracture determination target portion is obtained, the fracture limit stress and the re-yield stress are converted into an equivalent stress respectively, a fracture limit equivalent plastic strain corresponding to the fracture limit stress and an equivalent plastic strain corresponding to the re-yield stress are obtained from the respective equivalent stresses by using an equivalent stress-equivalent plastic strain curve based on a material of the metal structure, and a fracture risk of the fracture determination target portion is calculated using the fracture limit equivalent plastic strain and the equivalent plastic strain. a deformation analyzing step (S21, S22, S23) of performing deformation analysis from start of deformation to end of deformation of the metal structure; a fracture determination step (S24, S25, S26) of extracting a fracture determination target portion from a deformation state of the metal structure obtained in the deformation analyzing step (S21, S22, S23), and when the extracted fracture determination target portion has returned from a plastic state to an elastic state, given that a stress when the portion returned to the elastic state is (x, y) = (σ2, σ1) (maximum principal stress: σ1, minimum principal stress: σ2) on a (x, y) coordinate plane, and performing fracture determination of the fracture determination target portion using a re-yield stress determined by an intersection between a straight line satisfying a relation y = (σ1/σ2)x and an yield curve obtained from the plastic state of the fracture determination target portion, a fracture limit stress determined by an intersection between the straight line satisfying the relation y = (σ1/σ2)x and a fracture limit stress line of the fracture determination target portion is obtained, the fracture limit stress and the re-yield stress are converted into an equivalent stress respectively, a fracture limit equivalent plastic strain corresponding to the fracture limit stress and an equivalent plastic strain corresponding to the re-yield stress are obtained from the respective equivalent stresses by using an equivalent stress-equivalent plastic strain curve based on a material of the metal structure, and