A flexible printed circuit board according to an embodiment of the present invention includes an insulative base film; and a conductive pattern provided on at least one surface of the base film and including a wiring line including a bent portion having an angle of greater than or equal to 60° or a branched portion having an angle of greater than or equal to 60° in plan view. The wiring line is provided with a relaxation structure that relaxes stress concentration at the bent portion or the branched portion. The relaxation structure is structured such that the wiring line constitutes a wide wiring line or a dense wiring line group in a region in which a distance from the bent portion or the branched portion is less than or equal to 5 times a minimum width of the wiring line. The wide wiring line has a wiring line width that is greater than or equal to twice the minimum width of the wiring line. A ratio of a wiring line width to a wiring line interval of the dense wiring line group is greater than or equal to 1.5, and a total width of the dense wiring line group is greater than or equal to twice the minimum width of the wiring line.