A method of manufacturing a flexible printed circuit board including determining an elastic modulus of a conductive portion and an elastic modulus of first and second dielectric portions, determining a thickness of the conductive portion and the first and second dielectric portions so that a neutral plane is located within a predetermined range of the thickness of the conductive portion, the neutral plane being substantially free from tension or compression in response to bending of the flexible printed circuit board, and insulating the conductive portion according to the determined thickness and the determined elastic modulus.