An object of the invention is to provide a printed wiring board which is less likely to cause foaming even after a reflow step and in which a metal reinforcing plate is less likely to be peeled off, a manufacturing method thereof, and an electronic device. A printed wiring board (1) according to the present invention includes a wiring circuit board (6), a conductive adhesive layer (3), and a metal reinforcing plate (2). The conductive adhesive layer (3) is bonded to each of the wiring circuit board (6) and the metal reinforcing plate (2). The metal reinforcing plate (2) includes a nickel layer (2b) formed on a surface of a metal plate (2a). A ratio of a surface area of nickel hydroxide to nickel present in a surface of the nickel layer (2b) is more than 3 and equal to or less than 20.