A method of designing a blade of an axial flow fluid machine having an airfoil that is formed by a leading edge curve, a trailing edge curve, a pressure surface curve and a suction surface curve, comprising: a step of determining in a process using CFD the pressure surface curve as a curve being capable of first to third order differentiations at a connection point to the leading edge curve, that is, a pressure surface connection point; and a step of determining in a process using CFD the suction surface curve as a curve being capable of first to third order differentiations at a connection point to the leading edge curve, that is, a suction surface connection point; characterized in that the method further comprises: a step of selecting a first control point, a second control point, a third control point, a fourth control point, a fifth control point and a sixth control point that define a fifth order Bezier curve forming the leading edge curve, the step comprising: (C-1) a sub-step of designating the suction surface connection point as the first control point; (C-2) a sub-step of designating the pressure surface connection point as the sixth control point; provided that an intersection of a tangent to the pressure surface curve at the pressure surface connection point and a tangent to the suction surface curve at the suction surface connection point is referred to as a point ahead of the blade, (C-3) a sub-step of designating, as the second control point, a point that internally divides a line segment connecting the point ahead of the blade and the suction surface connection point with a ratio of p to (1-p) (where 0<p<1); (C-4) a sub-step of designating, as the fifth control point, a point that internally divides a line segment connecting the point ahead of the blade and the pressure surface connection point with a ratio of q to (1-q) (where 0<q<1); and (C-5) a sub-step of designating, as the third control point and the fourth control point, points having coordinates that are determined as solutions of simultaneous equations obtained by applying continuity conditions for first to third differential coefficients at the first control point and the sixth control point to a fifth order Bezier function that defines the fifth order Bezier curve. a step of determining in a process using CFD the pressure surface curve as a curve being capable of first to third order differentiations at a connection point to the leading edge curve, that is, a pressure surface connection point; and a step of determining in a process using CFD the suction surface curve as a curve being capable of first to third order differentiations at a connection point to the leading edge curve, that is, a suction surface connection point; (C-1) a sub-step of designating the suction surface connection point as the first control point; (C-2) a sub-step of designating the pressure surface connection point as the sixth control point; provided that an intersection of a tangent to the pressure surface curve at the pressure surface connection point and a tangent to the suction surface curve at the suction surface connection point is referred to as a point ahead of the blade, (C-3) a sub-step of designating, as the second control point, a point that internally divides a line segment connecting the point ahead of the blade and the suction surface connection point with a ratio of p to (1-p) (where 0<p<1); (C-4) a sub-step of designating, as the fifth control point, a point that internally divides a line segment connecting the point ahead of the blade and the pressure surface connection point with a ratio of q to (1-q) (where 0<q<1); and (C-5) a sub-step of designating, as the third control point and the fourth control point, points having coordinates that are determined as solutions of simultaneous equations obtained by applying continuity conditions for first to third differential coefficients at the first control point and the sixth control point to a fifth order Bezier function that defines the fifth order Bezier curve.