A fracture determination method for determining a fracture of a metal structure, the method comprising: a deformation analyzing step of performing deformation analysis from start of deformation to end of deformation of the metal structure; and a fracture determination step of extracting a fracture determination target portion from a deformation state of the metal structure obtained in the deformation analyzing step, 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 an (x, y) coordinate plane, 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, there are obtained: a coordinate point of an initial plastic stress determined by an intersection between the straight line satisfying the relation y = (σ1/σ2)x and an yield curve of an initial state of the fracture determination target portion; and a coordinate point of 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, and wherein a fracture risk of the fracture determination target portion is calculated using a distance from the coordinate point of the initial plastic stress to the coordinate point of the fracture limit stress and a distance from the coordinate point of the initial plastic stress to a coordinate point of the re-yield stress. a deformation analyzing step of performing deformation analysis from start of deformation to end of deformation of the metal structure; and a fracture determination step of extracting a fracture determination target portion from a deformation state of the metal structure obtained in the deformation analyzing step, 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 an (x, y) coordinate plane, 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, there are obtained: a coordinate point of an initial plastic stress determined by an intersection between the straight line satisfying the relation y = (σ1/σ2)x and an yield curve of an initial state of the fracture determination target portion; and a coordinate point of 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, and a coordinate point of an initial plastic stress determined by an intersection between the straight line satisfying the relation y = (σ1/σ2)x and an yield curve of an initial state of the fracture determination target portion; and a coordinate point of 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, and wherein a fracture risk of the fracture determination target portion is calculated using a distance from the coordinate point of the initial plastic stress to the coordinate point of the fracture limit stress and a distance from the coordinate point of the initial plastic stress to a coordinate point of the re-yield stress.