A non-photosensitive resin composition including: a self-cross-linkable copolymer having structural units of Formulae (1) and (2): wherein each R0 is independently a hydrogen atom or methyl group; X is an —O— group or an —NH— group; R1 is a single bond or a C1-6 alkylene group; R2 is a C1-6 alkyl group; a is an integer of 1 to 5, b is an integer of 0 to 4, and when a and b satisfy 1≦a+b≦5, and b is 2, 3, or 4, such R2 optionally differ from each other; R3 is a divalent organic group of Formula (I), Formula (II), or Formula (III), and R4 is an organic group having an epoxy group: wherein c is an integer of 0 to 3, d is an integer of 1 to 3, and each e is independently an integer of 2 to 6; and a solvent.